Bootstrapping Remote Secure Key Infrastructure (BRSKI)
RFC 8995

Document Type RFC - Proposed Standard (May 2021; No errata)
Authors Max Pritikin  , Michael Richardson  , Toerless Eckert  , Michael Behringer  , Kent Watsen 
Last updated 2021-05-21
Replaces draft-pritikin-anima-bootstrapping-keyinfra
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Internet Engineering Task Force (IETF)                       M. Pritikin
Request for Comments: 8995                                         Cisco
Category: Standards Track                                  M. Richardson
ISSN: 2070-1721                                 Sandelman Software Works
                                                               T. Eckert
                                                           Futurewei USA
                                                            M. Behringer
                                                                        
                                                               K. Watsen
                                                         Watsen Networks
                                                                May 2021

         Bootstrapping Remote Secure Key Infrastructure (BRSKI)

Abstract

   This document specifies automated bootstrapping of an Autonomic
   Control Plane.  To do this, a Secure Key Infrastructure is
   bootstrapped.  This is done using manufacturer-installed X.509
   certificates, in combination with a manufacturer's authorizing
   service, both online and offline.  We call this process the
   Bootstrapping Remote Secure Key Infrastructure (BRSKI) protocol.
   Bootstrapping a new device can occur when using a routable address
   and a cloud service, only link-local connectivity, or limited/
   disconnected networks.  Support for deployment models with less
   stringent security requirements is included.  Bootstrapping is
   complete when the cryptographic identity of the new key
   infrastructure is successfully deployed to the device.  The
   established secure connection can be used to deploy a locally issued
   certificate to the device as well.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8995.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
     1.1.  Prior Bootstrapping Approaches
     1.2.  Terminology
     1.3.  Scope of Solution
       1.3.1.  Support Environment
       1.3.2.  Constrained Environments
       1.3.3.  Network Access Controls
       1.3.4.  Bootstrapping is Not Booting
     1.4.  Leveraging the New Key Infrastructure / Next Steps
     1.5.  Requirements for Autonomic Networking Infrastructure (ANI)
           Devices
   2.  Architectural Overview
     2.1.  Behavior of a Pledge
     2.2.  Secure Imprinting Using Vouchers
     2.3.  Initial Device Identifier
       2.3.1.  Identification of the Pledge
       2.3.2.  MASA URI Extension
     2.4.  Protocol Flow
     2.5.  Architectural Components
       2.5.1.  Pledge
       2.5.2.  Join Proxy
       2.5.3.  Domain Registrar
       2.5.4.  Manufacturer Service
       2.5.5.  Public Key Infrastructure (PKI)
     2.6.  Certificate Time Validation
       2.6.1.  Lack of Real-Time Clock
       2.6.2.  Infinite Lifetime of IDevID
     2.7.  Cloud Registrar
     2.8.  Determining the MASA to Contact
   3.  Voucher-Request Artifact
     3.1.  Nonceless Voucher-Requests
     3.2.  Tree Diagram
     3.3.  Examples
     3.4.  YANG Module
   4.  Proxying Details (Pledge -- Proxy -- Registrar)
     4.1.  Pledge Discovery of Proxy
       4.1.1.  Proxy GRASP Announcements
     4.2.  CoAP Connection to Registrar
     4.3.  Proxy Discovery and Communication of Registrar
   5.  Protocol Details (Pledge -- Registrar -- MASA)
     5.1.  BRSKI-EST TLS Establishment Details
     5.2.  Pledge Requests Voucher from the Registrar
     5.3.  Registrar Authorization of Pledge
     5.4.  BRSKI-MASA TLS Establishment Details
       5.4.1.  MASA Authentication of Customer Registrar
     5.5.  Registrar Requests Voucher from MASA
       5.5.1.  MASA Renewal of Expired Vouchers
       5.5.2.  MASA Pinning of Registrar
       5.5.3.  MASA Check of the Voucher-Request Signature
       5.5.4.  MASA Verification of the Domain Registrar
       5.5.5.  MASA Verification of the Pledge
               'prior-signed-voucher-request'
       5.5.6.  MASA Nonce Handling
     5.6.  MASA and Registrar Voucher Response
       5.6.1.  Pledge Voucher Verification
       5.6.2.  Pledge Authentication of Provisional TLS Connection
     5.7.  Pledge BRSKI Status Telemetry
     5.8.  Registrar Audit-Log Request
       5.8.1.  MASA Audit-Log Response
       5.8.2.  Calculation of domainID
       5.8.3.  Registrar Audit-Log Verification
     5.9.  EST Integration for PKI Bootstrapping
       5.9.1.  EST Distribution of CA Certificates
       5.9.2.  EST CSR Attributes
       5.9.3.  EST Client Certificate Request
       5.9.4.  Enrollment Status Telemetry
       5.9.5.  Multiple Certificates
       5.9.6.  EST over CoAP
   6.  Clarification of Transfer-Encoding
   7.  Reduced Security Operational Modes
     7.1.  Trust Model
     7.2.  Pledge Security Reductions
     7.3.  Registrar Security Reductions
     7.4.  MASA Security Reductions
       7.4.1.  Issuing Nonceless Vouchers
       7.4.2.  Trusting Owners on First Use
       7.4.3.  Updating or Extending Voucher Trust Anchors
   8.  IANA Considerations
     8.1.  The IETF XML Registry
     8.2.  YANG Module Names Registry
     8.3.  BRSKI Well-Known Considerations
       8.3.1.  BRSKI .well-known Registration
       8.3.2.  BRSKI .well-known Registry
     8.4.  PKIX Registry
     8.5.  Pledge BRSKI Status Telemetry
     8.6.  DNS Service Names
     8.7.  GRASP Objective Names
   9.  Applicability to the Autonomic Control Plane (ACP)
     9.1.  Operational Requirements
       9.1.1.  MASA Operational Requirements
       9.1.2.  Domain Owner Operational Requirements
       9.1.3.  Device Operational Requirements
   10. Privacy Considerations
     10.1.  MASA Audit-Log
     10.2.  What BRSKI-EST Reveals
     10.3.  What BRSKI-MASA Reveals to the Manufacturer
     10.4.  Manufacturers and Used or Stolen Equipment
     10.5.  Manufacturers and Grey Market Equipment
     10.6.  Some Mitigations for Meddling by Manufacturers
     10.7.  Death of a Manufacturer
   11. Security Considerations
     11.1.  Denial of Service (DoS) against MASA
     11.2.  DomainID Must Be Resistant to Second-Preimage Attacks
     11.3.  Availability of Good Random Numbers
     11.4.  Freshness in Voucher-Requests
     11.5.  Trusting Manufacturers
     11.6.  Manufacturer Maintenance of Trust Anchors
       11.6.1.  Compromise of Manufacturer IDevID Signing Keys
       11.6.2.  Compromise of MASA Signing Keys
       11.6.3.  Compromise of MASA Web Service
     11.7.  YANG Module Security Considerations
   12. References
     12.1.  Normative References
     12.2.  Informative References
   Appendix A.  IPv4 and Non-ANI Operations
     A.1.  IPv4 Link-Local Addresses
     A.2.  Use of DHCPv4
   Appendix B.  mDNS / DNS-SD Proxy Discovery Options
   Appendix C.  Example Vouchers
     C.1.  Keys Involved
       C.1.1.  Manufacturer Certification Authority for IDevID
               Signatures
       C.1.2.  MASA Key Pair for Voucher Signatures
       C.1.3.  Registrar Certification Authority
       C.1.4.  Registrar Key Pair
       C.1.5.  Pledge Key Pair
     C.2.  Example Process
       C.2.1.  Pledge to Registrar
       C.2.2.  Registrar to MASA
       C.2.3.  MASA to Registrar
       Acknowledgements
   Authors' Addresses

1.  Introduction

   The Bootstrapping Remote Secure Key Infrastructure (BRSKI) protocol
   provides a solution for secure zero-touch (automated) bootstrap of
   new (unconfigured) devices that are called "pledges" in this
   document.  Pledges have an Initial Device Identifier (IDevID)
   installed in them at the factory.

   "BRSKI", pronounced like "brewski", is a colloquial term for beer in
   Canada and parts of the Midwestern United States [brewski].

   This document primarily provides for the needs of the ISP and
   enterprise-focused Autonomic Networking Integrated Model and Approach
   (ANIMA) Autonomic Control Plane (ACP) [RFC8994].  This bootstrap
   process satisfies the requirement of making all operations secure by
   default per Section 3.3 of [RFC7575].  Other users of the BRSKI
   protocol will need to provide separate applicability statements that
   include privacy and security considerations appropriate to that
   deployment.  Section 9 explains the detailed applicability for this
   ACP usage.

   The BRSKI protocol requires a significant amount of communication
   between manufacturer and owner: in its default modes, it provides a
   cryptographic transfer of control to the initial owner.  In its
   strongest modes, it leverages sales channel information to identify
   the owner in advance.  Resale of devices is possible, provided that
   the manufacturer is willing to authorize the transfer.  Mechanisms to
   enable transfers of ownership without manufacturer authorization are
   not included in this version of the protocol, but it could be
   designed into future versions.

   This document describes how a pledge discovers (or are discovered by)
   an element of the network domain that it will belong to and that will
   perform its bootstrap.  This element (device) is called the
   "registrar".  Before any other operation, the pledge and registrar
   need to establish mutual trust:

   1.  Registrar authenticating the pledge: "Who is this device?  What
       is its identity?"

   2.  Registrar authorizing the pledge: "Is it mine?  Do I want it?
       What are the chances it has been compromised?"

   3.  Pledge authenticating the registrar: "What is this registrar's
       identity?"

   4.  Pledge authorizing the registrar: "Should I join this network?"

   This document details protocols and messages to answer the above
   questions.  It uses a TLS connection and a PKIX-shaped (X.509v3)
   certificate (an IEEE 802.1AR IDevID [IDevID]) of the pledge to answer
   points 1 and 2.  It uses a new artifact called a "voucher" that the
   registrar receives from a Manufacturer Authorized Signing Authority
   (MASA) and passes it to the pledge to answer points 3 and 4.

   A proxy provides very limited connectivity between the pledge and the
   registrar.

   The syntactic details of vouchers are described in detail in
   [RFC8366].  This document details automated protocol mechanisms to
   obtain vouchers, including the definition of a "voucher-request"
   message that is a minor extension to the voucher format (see
   Section 3) as defined by [RFC8366].

   BRSKI results in the pledge storing an X.509 root certificate
   sufficient for verifying the registrar identity.  In the process, a
   TLS connection is established that can be directly used for
   Enrollment over Secure Transport (EST).  In effect, BRSKI provides an
   automated mechanism for "Bootstrap Distribution of CA Certificates"
   described in [RFC7030], Section 4.1.1, wherein the pledge "MUST [...]
   engage a human user to authorize the CA certificate using out-of-band
   data".  With BRSKI, the pledge now can automate this process using
   the voucher.  Integration with a complete EST enrollment is optional
   but trivial.

   BRSKI is agile enough to support bootstrapping alternative key
   infrastructures, such as a symmetric key solution, but no such system
   is described in this document.

1.1.  Prior Bootstrapping Approaches

   To literally "pull yourself up by the bootstraps" is an impossible
   action.  Similarly, the secure establishment of a key infrastructure
   without external help is also an impossibility.  Today, it is
   commonly accepted that the initial connections between nodes are
   insecure, until key distribution is complete, or that domain-specific
   keying material (often pre-shared keys, including mechanisms like
   Subscriber Identification Module (SIM) cards) is pre-provisioned on
   each new device in a costly and non-scalable manner.  Existing
   automated mechanisms are known as non-secured "Trust on First Use
   (TOFU)" [RFC7435], "resurrecting duckling"
   [Stajano99theresurrecting], or "pre-staging".

   Another prior approach has been to try and minimize user actions
   during bootstrapping, but not eliminate all user actions.  The
   original EST protocol [RFC7030] does reduce user actions during
   bootstrapping but does not provide solutions for how the following
   protocol steps can be made autonomic (not involving user actions):

   *  using the Implicit Trust Anchor (TA) [RFC7030] database to
      authenticate an owner-specific service (not an autonomic solution
      because the URL must be securely distributed),

   *  engaging a human user to authorize the CA certificate using out-
      of-band data (not an autonomic solution because the human user is
      involved),

   *  using a configured Explicit TA database (not an autonomic solution
      because the distribution of an explicit TA database is not
      autonomic), and

   *  using a certificate-less TLS mutual authentication method (not an
      autonomic solution because the distribution of symmetric key
      material is not autonomic).

   These "touch" methods do not meet the requirements for zero-touch.

   There are "call home" technologies where the pledge first establishes
   a connection to a well-known manufacturer service using a common
   client-server authentication model.  After mutual authentication,
   appropriate credentials to authenticate the target domain are
   transferred to the pledge.  This creates several problems and
   limitations:

   *  the pledge requires real-time connectivity to the manufacturer
      service,

   *  the domain identity is exposed to the manufacturer service (this
      is a privacy concern), and

   *  the manufacturer is responsible for making the authorization
      decisions (this is a liability concern).

   BRSKI addresses these issues by defining extensions to the EST
   protocol for the automated distribution of vouchers.

1.2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The following terms are defined for clarity:

   ANI:  The Autonomic Networking Infrastructure as defined by
      [RFC8993].  Section 9 details specific requirements for pledges,
      proxies, and registrars when they are part of an ANI.

   Circuit Proxy:  A stateful implementation of the Join Proxy.  This is
      the assumed type of proxy.

   drop-ship:  The physical distribution of equipment containing the
      "factory default" configuration to a final destination.  In zero-
      touch scenarios, there is no staging or preconfiguration during
      drop-ship.

   Domain:  The set of entities that share a common local trust anchor.
      This includes the proxy, registrar, domain CA, management
      components, and any existing entity that is already a member of
      the domain.

   Domain CA:  The domain Certification Authority (CA) provides
      certification functionalities to the domain.  At a minimum, it
      provides certification functionalities to a registrar and manages
      the private key that defines the domain.  Optionally, it certifies
      all elements.

   domainID:  The domain IDentity is a unique value based upon the
      registrar's CA certificate.  Section 5.8.2 specifies how it is
      calculated.

   enrollment:  The process where a device presents key material to a
      network and acquires a network-specific identity.  For example,
      when a certificate signing request is presented to a CA, and a
      certificate is obtained in response.

   IDevID:  An Initial Device Identifier X.509 certificate installed by
      the vendor on new equipment.  This is a term from 802.1AR
      [IDevID].

   imprint:  The process where a device obtains the cryptographic key
      material to identify and trust future interactions with a network.
      This term is taken from Konrad Lorenz's work in biology with new
      ducklings: during a critical period, the duckling would assume
      that anything that looks like a mother duck is in fact their
      mother.  An equivalent for a device is to obtain the fingerprint
      of the network's root CA certificate.  A device that imprints on
      an attacker suffers a similar fate to a duckling that imprints on
      a hungry wolf.  Securely imprinting is a primary focus of this
      document [imprinting].  The analogy to Lorenz's work was first
      noted in [Stajano99theresurrecting].

   IPIP Proxy:  A stateless proxy alternative.

   Join Proxy:  A domain entity that helps the pledge join the domain.
      A Join Proxy facilitates communication for devices that find
      themselves in an environment where they are not provided
      connectivity until after they are validated as members of the
      domain.  For simplicity, this document sometimes uses the term of
      "proxy" to indicate the Join Proxy.  The pledge is unaware that
      they are communicating with a proxy rather than directly with a
      registrar.

   Join Registrar (and Coordinator):  A representative of the domain
      that is configured, perhaps autonomically, to decide whether a new
      device is allowed to join the domain.  The administrator of the
      domain interfaces with a "Join Registrar (and Coordinator)" to
      control this process.  Typically, a Join Registrar is "inside" its
      domain.  For simplicity, this document often refers to this as
      just "registrar".  Within [RFC8993], it is referred to as the
      "Join Registrar Autonomic Service Agent (ASA)".  Other communities
      use the abbreviation "JRC".

   LDevID:  A Local Device Identifier X.509 certificate installed by the
      owner of the equipment.  This is a term from 802.1AR [IDevID].

   manufacturer:  The term manufacturer is used throughout this document
      as the entity that created the device.  This is typically the
      original equipment manufacturer (OEM), but in more complex
      situations, it could be a value added retailer (VAR), or possibly
      even a systems integrator.  In general, a goal of BRSKI is to
      eliminate small distinctions between different sales channels.
      The reason for this is that it permits a single device, with a
      uniform firmware load, to be shipped directly to all customers.
      This eliminates costs for the manufacturer.  This also reduces the
      number of products supported in the field, increasing the chance
      that firmware will be more up to date.

   MASA Audit-Log:  An anonymized list of previous owners maintained by
      the MASA on a per-device (per-pledge) basis, as described in
      Section 5.8.1.

   MASA Service:  A third-party MASA service on the global Internet.
      The MASA signs vouchers.  It also provides a repository for audit-
      log information of privacy-protected bootstrapping events.  It
      does not track ownership.

   nonced:  A voucher (or request) that contains a nonce (the normal
      case).

   nonceless:  A voucher (or request) that does not contain a nonce and
      either relies upon accurate clocks for expiration or does not
      expire.

   offline:  When an architectural component cannot perform real-time
      communications with a peer, due to either network connectivity or
      the peer being turned off, the operation is said to be occurring
      offline.

   Ownership Tracker:  An Ownership Tracker service on the global
      Internet.  The Ownership Tracker uses business processes to
      accurately track ownership of all devices shipped against domains
      that have purchased them.  Although optional, this component
      allows vendors to provide additional value in cases where their
      sales and distribution channels allow for accurate tracking of
      such ownership.  Tracking information about ownership is indicated
      in vouchers, as described in [RFC8366].

   Pledge:  The prospective (unconfigured) device, which has an identity
      installed at the factory.

   (Public) Key Infrastructure:  The collection of systems and processes
      that sustains the activities of a public key system.  The
      registrar acts as a "Registration Authority"; see [RFC5280] and
      Section 7 of [RFC5272].

   TOFU:  Trust on First Use. Used similarly to how it is described in
      [RFC7435].  This is where a pledge device makes no security
      decisions but rather simply trusts the first registrar it is
      contacted by.  This is also known as the "resurrecting duckling"
      model.

   Voucher:  A signed artifact from the MASA that indicates the
      cryptographic identity of the registrar it should trust to a
      pledge.  There are different types of vouchers depending on how
      that trust is asserted.  Multiple voucher types are defined in
      [RFC8366].

1.3.  Scope of Solution

1.3.1.  Support Environment

   This solution (BRSKI) can support large router platforms with multi-
   gigabit inter-connections, mounted in controlled access data centers.
   But this solution is not exclusive to large equipment: it is intended
   to scale to thousands of devices located in hostile environments,
   such as ISP-provided Customer Premises Equipment (CPE) devices that
   are drop-shipped to the end user.  The situation where an order is
   fulfilled from a distributed warehouse from a common stock and
   shipped directly to the target location at the request of a domain
   owner is explicitly supported.  That stock ("SKU") could be provided
   to a number of potential domain owners, and the eventual domain owner
   will not know a priori which device will go to which location.

   The bootstrapping process can take minutes to complete depending on
   the network infrastructure and device processing speed.  The network
   communication itself is not optimized for speed; for privacy reasons,
   the discovery process allows for the pledge to avoid announcing its
   presence through broadcasting.

   Nomadic or mobile devices often need to acquire credentials to access
   the network at the new location.  An example of this is mobile phone
   roaming among network operators, or even between cell towers.  This
   is usually called "handoff".  BRSKI does not provide a low-latency
   handoff, which is usually a requirement in such situations.  For
   these solutions, BRSKI can be used to create a relationship (an
   LDevID) with the "home" domain owner.  The resulting credentials are
   then used to provide credentials more appropriate for a low-latency
   handoff.

1.3.2.  Constrained Environments

   Questions have been posed as to whether this solution is suitable in
   general for Internet of Things (IoT) networks.  This depends on the
   capabilities of the devices in question.  The terminology of
   [RFC7228] is best used to describe the boundaries.

   The solution described in this document is aimed in general at non-
   constrained (i.e., Class 2+ [RFC7228]) devices operating on a non-
   challenged network.  The entire solution as described here is not
   intended to be usable as is by constrained devices operating on
   challenged networks (such as 802.15.4 Low-Power and Lossy Networks
   (LLNs)).

   Specifically, there are protocol aspects described here that might
   result in congestion collapse or energy exhaustion of intermediate
   battery-powered routers in an LLN.  Those types of networks should
   not use this solution.  These limitations are predominately related
   to the large credential and key sizes required for device
   authentication.  Defining symmetric key techniques that meet the
   operational requirements is out of scope, but the underlying protocol
   operations (TLS handshake and signing structures) have sufficient
   algorithm agility to support such techniques when defined.

   The imprint protocol described here could, however, be used by non-
   energy constrained devices joining a non-constrained network (for
   instance, smart light bulbs are usually mains powered and use 802.11
   wireless technology).  It could also be used by non-constrained
   devices across a non-energy constrained, but challenged, network
   (such as 802.15.4).  The certificate contents, and the process by
   which the four questions above are resolved, do apply to constrained
   devices.  It is simply the actual on-the-wire imprint protocol that
   could be inappropriate.

1.3.3.  Network Access Controls

   This document presumes that network access control has already
   occurred, is not required, or is integrated by the proxy and
   registrar in such a way that the device itself does not need to be
   aware of the details.  Although the use of an X.509 IDevID is
   consistent with IEEE 802.1AR [IDevID], and allows for alignment with
   802.1X network access control methods, its use here is for pledge
   authentication rather than network access control.  Integrating this
   protocol with network access control, perhaps as an Extensible
   Authentication Protocol (EAP) method (see [RFC3748]), is out of scope
   for this document.

1.3.4.  Bootstrapping is Not Booting

   This document describes "bootstrapping" as the protocol used to
   obtain a local trust anchor.  It is expected that this trust anchor,
   along with any additional configuration information subsequently
   installed, is persisted on the device across system restarts
   ("booting").  Bootstrapping occurs only infrequently such as when a
   device is transferred to a new owner or has been reset to factory
   default settings.

1.4.  Leveraging the New Key Infrastructure / Next Steps

   As a result of the protocol described herein, bootstrapped devices
   have the domain CA trust anchor in common.  An end-entity (EE)
   certificate has optionally been issued from the domain CA.  This
   makes it possible to securely deploy functionalities across the
   domain; for example:

   *  Device management

   *  Routing authentication

   *  Service discovery

   The major intended benefit is the ability to use the credentials
   deployed by this protocol to secure the Autonomic Control Plane (ACP)
   [RFC8994].

1.5.  Requirements for Autonomic Networking Infrastructure (ANI) Devices

   The BRSKI protocol can be used in a number of environments.  Some of
   the options in this document are the result of requirements that are
   out of the ANI scope.  This section defines the base requirements for
   ANI devices.

   For devices that intend to become part of an ANI [RFC8993] that
   includes an Autonomic Control Plane [RFC8994], the BRSKI protocol
   MUST be implemented.

   The pledge must perform discovery of the proxy as described in
   Section 4.1 using the Discovery Unsolicited Link-Local (DULL)
   [RFC8990] M_FLOOD announcements of the GeneRic Autonomic Signaling
   Protocol (GRASP).

   Upon successfully validating a voucher artifact, a status telemetry
   MUST be returned; see Section 5.7.

   An ANIMA ANI pledge MUST implement the EST automation extensions
   described in Section 5.9.  They supplement the EST [RFC7030] to
   better support automated devices that do not have an end user.

   The ANI Join Registrar ASA MUST support all the BRSKI and above-
   listed EST operations.

   All ANI devices SHOULD support the BRSKI proxy function, using
   Circuit Proxies over the Autonomic Control Plane (ACP) (see
   Section 4.3).

2.  Architectural Overview

   The logical elements of the bootstrapping framework are described in
   this section.  Figure 1 provides a simplified overview of the
   components.

                                              +------------------------+
      +--------------Drop-Ship----------------| Vendor Service         |
      |                                       +------------------------+
      |                                       | M anufacturer|         |
      |                                       | A uthorized  |Ownership|
      |                                       | S igning     |Tracker  |
      |                                       | A uthority   |         |
      |                                       +--------------+---------+
      |                                                      ^
      |                                                      |  BRSKI-
      V                                                      |   MASA
   +-------+     ............................................|...
   |       |     .                                           |  .
   |       |     .  +------------+       +-----------+       |  .
   |       |     .  |            |       |           |       |  .
   |Pledge |     .  |   Join     |       | Domain    <-------+  .
   |       |     .  |   Proxy    |       | Registrar |          .
   |       <-------->............<-------> (PKI RA)  |          .
   |       |        |        BRSKI-EST   |           |          .
   |       |     .  |            |       +-----+-----+          .
   |IDevID |     .  +------------+             | e.g., RFC 7030 .
   |       |     .           +-----------------+----------+     .
   |       |     .           | Key Infrastructure         |     .
   |       |     .           | (e.g., PKI CA)             |     .
   +-------+     .           |                            |     .
                 .           +----------------------------+     .
                 .                                              .
                 ................................................
                               "Domain" Components

                      Figure 1: Architecture Overview

   We assume a multivendor network.  In such an environment, there could
   be a manufacturer service for each manufacturer that supports devices
   following this document's specification, or an integrator could
   provide a generic service authorized by multiple manufacturers.  It
   is unlikely that an integrator could provide ownership tracking
   services for multiple manufacturers due to the required sales channel
   integrations necessary to track ownership.

   The domain is the managed network infrastructure with a key
   infrastructure that the pledge is joining.  The domain provides
   initial device connectivity sufficient for bootstrapping through a
   proxy.  The domain registrar authenticates the pledge, makes
   authorization decisions, and distributes vouchers obtained from the
   manufacturer service.  Optionally, the registrar also acts as a PKI
   CA.

2.1.  Behavior of a Pledge

   The pledge goes through a series of steps, which are outlined here at
   a high level.

                  ------------
                 /  Factory   \
                 \  default   /
                  -----+------
                       |
                +------v-------+
                | (1) Discover |
   +------------>              |
   |            +------+-------+
   |                   |
   |            +------v-------+
   |            | (2) Identify |
   ^------------+              |
   | rejected   +------+-------+
   |                   |
   |            +------v-------+
   |            | (3) Request  |
   |            |     Join     |
   |            +------+-------+
   |                   |
   |            +------v-------+
   |            | (4) Imprint  |
   ^------------+              |
   | Bad MASA   +------+-------+
   | response          |  send Voucher Status Telemetry
   |            +------v-------+
   |            | (5) Enroll   |<---+ (non-error HTTP codes)
   ^------------+              |\___/ (e.g., 202 "Retry-After")
   | Enroll     +------+-------+
   | failure           |
   |              -----v------
   |             /  Enrolled  \
   ^------------+             |
    Factory      \------------/
    reset

                       Figure 2: Pledge State Diagram

   State descriptions for the pledge are as follows:

   1.  Discover a communication channel to a registrar.

   2.  Identify itself.  This is done by presenting an X.509 IDevID
       credential to the discovered registrar (via the proxy) in a TLS
       handshake.  (The registrar credentials are only provisionally
       accepted at this time.)

   3.  Request to join the discovered registrar.  A unique nonce is
       included, ensuring that any responses can be associated with this
       particular bootstrapping attempt.

   4.  Imprint on the registrar.  This requires verification of the
       manufacturer-service-provided voucher.  A voucher contains
       sufficient information for the pledge to complete authentication
       of a registrar.  This document details this step in depth.

   5.  Enroll.  After imprint, an authenticated TLS (HTTPS) connection
       exists between the pledge and registrar.  EST [RFC7030] can then
       be used to obtain a domain certificate from a registrar.

   The pledge is now a member of, and can be managed by, the domain and
   will only repeat the discovery aspects of bootstrapping if it is
   returned to factory default settings.

   This specification details integration with EST enrollment so that
   pledges can optionally obtain a locally issued certificate, although
   any Representational State Transfer (REST) (see [REST]) interface
   could be integrated in future work.

2.2.  Secure Imprinting Using Vouchers

   A voucher is a cryptographically protected artifact (using a digital
   signature) to the pledge device authorizing a zero-touch imprint on
   the registrar domain.

   The format and cryptographic mechanism of vouchers is described in
   detail in [RFC8366].

   Vouchers provide a flexible mechanism to secure imprinting: the
   pledge device only imprints when a voucher can be validated.  At the
   lowest security levels, the MASA can indiscriminately issue vouchers
   and log claims of ownership by domains.  At the highest security
   levels, issuance of vouchers can be integrated with complex sales
   channel integrations that are beyond the scope of this document.  The
   sales channel integration would verify actual (legal) ownership of
   the pledge by the domain.  This provides the flexibility for a number
   of use cases via a single common protocol mechanism on the pledge and
   registrar devices that are to be widely deployed in the field.  The
   MASA services have the flexibility to either leverage the currently
   defined claim mechanisms or experiment with higher or lower security
   levels.

   Vouchers provide a signed but non-encrypted communication channel
   among the pledge, the MASA, and the registrar.  The registrar
   maintains control over the transport and policy decisions, allowing
   the local security policy of the domain network to be enforced.

2.3.  Initial Device Identifier

   Pledge authentication and pledge voucher-request signing is via a
   PKIX-shaped certificate installed during the manufacturing process.
   This is the 802.1AR IDevID, and it provides a basis for
   authenticating the pledge during the protocol exchanges described
   here.  There is no requirement for a common root PKI hierarchy.  Each
   device manufacturer can generate its own root certificate.
   Specifically, the IDevID enables:

   *  Uniquely identifying the pledge by the Distinguished Name (DN) and
      subjectAltName (SAN) parameters in the IDevID.  The unique
      identification of a pledge in the voucher objects are derived from
      those parameters as described below.  Section 10.3 discusses
      privacy implications of the identifier.

   *  Providing a cryptographic authentication of the pledge to the
      registrar (see Section 5.3).

   *  Securing auto-discovery of the pledge's MASA by the registrar (see
      Section 2.8).

   *  Signing of a voucher-request by the pledge's IDevID (see
      Section 3).

   *  Providing a cryptographic authentication of the pledge to the MASA
      (see Section 5.5.5).

   Sections 7.2.13 (2009 edition) and 8.10.3 (2018 edition) of [IDevID]
   discuss keyUsage and extendedKeyUsage extensions in the IDevID
   certificate.  [IDevID] acknowledges that adding restrictions in the
   certificate limits applicability of these long-lived certificates.
   This specification emphasizes this point and therefore RECOMMENDS
   that no key usage restrictions be included.  This is consistent with
   [RFC5280], Section 4.2.1.3, which does not require key usage
   restrictions for end-entity certificates.

2.3.1.  Identification of the Pledge

   In the context of BRSKI, pledges have a 1:1 relationship with a
   "serial-number".  This serial-number is used both in the serial-
   number field of a voucher or voucher-requests (see Section 3) and in
   local policies on the registrar or MASA (see Section 5).

   There is a (certificate) serialNumber field defined in [RFC5280],
   Section 4.1.2.2.  In ASN.1, this is referred to as the
   CertificateSerialNumber.  This field is NOT relevant to this
   specification.  Do not confuse this field with the serial-number
   defined by this document, or by [IDevID] and [RFC4519], Section 2.31.

   The device serial number is defined in Appendix A.1 of [RFC5280] as
   the X520SerialNumber, with the OID tag id-at-serialNumber.

   The device _serialNumber_ field (X520SerialNumber) is used as follows
   by the pledge to build the *serial-number* that is placed in the
   voucher-request.  In order to build it, the fields need to be
   converted into a serial-number of "type string".

   An example of a printable form of the serialNumber field is provided
   in [RFC4519], Section 2.31 ("WI-3005").  That section further
   provides equality and syntax attributes.

   Due to the reality of existing device identity provisioning
   processes, some manufacturers have stored serial-numbers in other
   fields.  Registrars SHOULD be configurable, on a per-manufacturer
   basis, to look for serial-number equivalents in other fields.

   As explained in Section 5.5, the registrar MUST again extract the
   serialNumber itself from the pledge's TLS certificate.  It can
   consult the serial-number in the pledge request if there is any
   possible confusion about the source of the serial-number.

2.3.2.  MASA URI Extension

   This document defines a new PKIX non-critical certificate extension
   to carry the MASA URI.  This extension is intended to be used in the
   IDevID certificate.  The URI is represented as described in
   Section 7.4 of [RFC5280].

   The URI provides the authority information.  The BRSKI "/.well-known"
   tree [RFC8615] is described in Section 5.

   A complete URI MAY be in this extension, including the "scheme",
   "authority", and "path".  The complete URI will typically be used in
   diagnostic or experimental situations.  Typically (and in
   consideration to constrained systems), this SHOULD be reduced to only
   the "authority", in which case a scheme of "https://" (see [RFC7230],
   Section 2.7.3) and a "path" of "/.well-known/brski" is to be assumed.

   The registrar can assume that only the "authority" is present in the
   extension, if there are no slash ("/") characters in the extension.

   Section 7.4 of [RFC5280] calls out various schemes that MUST be
   supported, including the Lightweight Directory Access Protocol
   (LDAP), HTTP, and FTP.  However, the registrar MUST use HTTPS for the
   BRSKI-MASA connection.

   The new extension is identified as follows:

   <CODE BEGINS>
   MASAURLExtnModule-2016 { iso(1) identified-organization(3) dod(6)
   internet(1) security(5) mechanisms(5) pkix(7)
   id-mod(0) id-mod-MASAURLExtn2016(96) }

   DEFINITIONS IMPLICIT TAGS ::= BEGIN

   -- EXPORTS ALL --

   IMPORTS
   EXTENSION
   FROM PKIX-CommonTypes-2009
     { iso(1) identified-organization(3) dod(6) internet(1)
       security(5) mechanisms(5) pkix(7) id-mod(0)
       id-mod-pkixCommon-02(57) }

   id-pe FROM PKIX1Explicit-2009
     { iso(1) identified-organization(3) dod(6) internet(1)
        security(5) mechanisms(5) pkix(7) id-mod(0)
        id-mod-pkix1-explicit-02(51) } ;

   MASACertExtensions EXTENSION ::= { ext-MASAURL, ... }
   ext-MASAURL EXTENSION ::= { SYNTAX MASAURLSyntax
   IDENTIFIED BY id-pe-masa-url }

   id-pe-masa-url OBJECT IDENTIFIER ::= { id-pe 32 }

   MASAURLSyntax ::= IA5String

   END
   <CODE ENDS>

                       Figure 3: MASAURL ASN.1 Module

   The choice of id-pe is based on guidance found in Section 4.2.2 of
   [RFC5280]: "These extensions may be used to direct applications to
   on-line information about the issuer or the subject".  The MASA URL
   is precisely that: online information about the particular subject.

2.4.  Protocol Flow

   A representative flow is shown in Figure 4.

   +--------+         +---------+    +------------+     +------------+
   | Pledge |         | Circuit |    | Domain     |     | Vendor     |
   |        |         | Join    |    | Registrar  |     | Service    |
   |        |         | Proxy   |    |  (JRC)     |     | (MASA)     |
   +--------+         +---------+    +------------+     +------------+
     |                     |                   |           Internet |
   [discover]              |                   |                    |
     |<-RFC 4862 IPv6 addr |                   |                    |
     |<-RFC 3927 IPv4 addr | Appendix A        |  Legend            |
     |-++++++++++++++++++->|                   | C - Circuit        |
     | optional: mDNS query| Appendix B        |     Join Proxy     |
     | RFCs 6763/6762 (+)  |                   | P - Provisional TLS|
     |<-++++++++++++++++++-|                   |     Connection     |
     | GRASP M_FLOOD       |                   |                    |
     |   periodic broadcast|                   |                    |
   [identity]              |                   |                    |
     |<------------------->C<----------------->|                    |
     |         TLS via the Join Proxy          |                    |
     |<--Registrar TLS server authentication---|                    |
   [PROVISIONAL accept of server cert]         |                    |
     P---X.509 client authentication---------->|                    |
   [request join]                              |                    |
     P---Voucher-Request(w/nonce for voucher)->|                    |
     P                  /-------------------   |                    |
     P                  |                 [accept device?]          |
     P                  |                 [contact vendor]          |
     P                  |                      |--Pledge ID-------->|
     P                  |                      |--Domain ID-------->|
     P                  |                      |--optional:nonce--->|
     P              optional:                  |     [extract DomainID]
     P        can occur in advance             |     [update audit-log]
     P            if nonceless                 |                    |
     P                  |                      |<- voucher ---------|
     P                  \-------------------   | w/nonce if provided|
     P<------voucher---------------------------|                    |
   [imprint]                                   |                    |
     |-------voucher status telemetry--------->|                    |
     |                                         |<-device audit-log--|
     |                             [verify audit-log and voucher]   |
     |<--------------------------------------->|                    |
   [enroll]                                    |                    |
     | Continue with enrollment using now      |                    |
     | bidirectionally authenticated TLS       |                    |
     | session per RFC 7030.                   |                    |
   [enrolled]                                  |                    |

                  Figure 4: Protocol Time Sequence Diagram

   On initial bootstrap, a new device (the pledge) uses a local service
   auto-discovery (the GeneRic Autonomic Signaling Protocol (GRASP) or
   Multicast DNS (mDNS)) to locate a Join Proxy.  The Join Proxy
   connects the pledge to a local registrar (the JRC).

   Having found a candidate registrar, the fledgling pledge sends some
   information about itself to the registrar, including its serial
   number in the form of a voucher-request and its IDevID certificate as
   part of the TLS session.

   The registrar can determine whether it expected such a device to
   appear and locates a MASA.  The location of the MASA is usually found
   in an extension in the IDevID.  Having determined that the MASA is
   suitable, the entire information from the initial voucher-request
   (including the device's serial number) is transmitted over the
   Internet in a TLS-protected channel to the manufacturer, along with
   information about the registrar/owner.

   The manufacturer can then apply policy based on the provided
   information, as well as other sources of information (such as sales
   records), to decide whether to approve the claim by the registrar to
   own the device; if the claim is accepted, a voucher is issued that
   directs the device to accept its new owner.

   The voucher is returned to the registrar, but not immediately to the
   device -- the registrar has an opportunity to examine the voucher,
   the MASA's audit-logs, and other sources of information to determine
   whether the device has been tampered with and whether the bootstrap
   should be accepted.

   No filtering of information is possible in the signed voucher, so
   this is a binary yes-or-no decision.  After the registrar has applied
   any local policy to the voucher, if it accepts the voucher, then the
   voucher is returned to the pledge for imprinting.

   The voucher also includes a trust anchor that the pledge uses to
   represent the owner.  This is used to successfully bootstrap from an
   environment where only the manufacturer has built-in trust by the
   device to an environment where the owner now has a PKI footprint on
   the device.

   When BRSKI is followed with EST, this single footprint is further
   leveraged into the full owner's PKI and an LDevID for the device.
   Subsequent reporting steps provide flows of information to indicate
   success/failure of the process.

2.5.  Architectural Components

2.5.1.  Pledge

   The pledge is the device that is attempting to join.  It is assumed
   that the pledge talks to the Join Proxy using link-local network
   connectivity.  In most cases, the pledge has no other connectivity
   until the pledge completes the enrollment process and receives some
   kind of network credential.

2.5.2.  Join Proxy

   The Join Proxy provides HTTPS connectivity between the pledge and the
   registrar.  A Circuit Proxy mechanism is described in Section 4.
   Additional mechanisms, including a Constrained Application Protocol
   (CoAP) mechanism and a stateless IP in IP (IPIP) mechanism, are the
   subject of future work.

2.5.3.  Domain Registrar

   The domain's registrar operates as the BRSKI-MASA client when
   requesting vouchers from the MASA (see Section 5.4).  The registrar
   operates as the BRSKI-EST server when pledges request vouchers (see
   Section 5.1).  The registrar operates as the BRSKI-EST server
   "Registration Authority" if the pledge requests an end-entity
   certificate over the BRSKI-EST connection (see Section 5.9).

   The registrar uses an Implicit Trust Anchor database for
   authenticating the BRSKI-MASA connection's MASA TLS server
   certificate.  Configuration or distribution of trust anchors is out
   of scope for this specification.

   The registrar uses a different Implicit Trust Anchor database for
   authenticating the BRSKI-EST connection's pledge TLS Client
   Certificate.  Configuration or distribution of the BRSKI-EST client
   trust anchors is out of scope of this specification.  Note that the
   trust anchors in / excluded from the database will affect which
   manufacturers' devices are acceptable to the registrar as pledges,
   and they can also be used to limit the set of MASAs that are trusted
   for enrollment.

2.5.4.  Manufacturer Service

   The manufacturer service provides two logically separate functions:
   the MASA as described in Sections 5.5 and 5.6 and an ownership
   tracking/auditing function as described in Sections 5.7 and 5.8.

2.5.5.  Public Key Infrastructure (PKI)

   The Public Key Infrastructure (PKI) administers certificates for the
   domain of concern, providing the trust anchor(s) for it and allowing
   enrollment of pledges with domain certificates.

   The voucher provides a method for the distribution of a single PKI
   trust anchor (as the "pinned-domain-cert").  A distribution of the
   full set of current trust anchors is possible using the optional EST
   integration.

   The domain's registrar acts as a Registration Authority [RFC5272],
   requesting certificates for pledges from the PKI.

   The expectations of the PKI are unchanged from EST [RFC7030].  This
   document does not place any additional architectural requirements on
   the PKI.

2.6.  Certificate Time Validation

2.6.1.  Lack of Real-Time Clock

   When bootstrapping, many devices do not have knowledge of the current
   time.  Mechanisms such as Network Time Protocols cannot be secured
   until bootstrapping is complete.  Therefore, bootstrapping is defined
   with a framework that does not require knowledge of the current time.
   A pledge MAY ignore all time stamps in the voucher and in the
   certificate validity periods if it does not know the current time.

   The pledge is exposed to dates in the following five places:
   registrar certificate notBefore, registrar certificate notAfter,
   voucher created-on, and voucher expires-on.  Additionally,
   Cryptographic Message Syntax (CMS) signatures contain a signingTime.

   A pledge with a real-time clock in which it has confidence MUST check
   the above time fields in all certificates and signatures that it
   processes.

   If the voucher contains a nonce, then the pledge MUST confirm the
   nonce matches the original pledge voucher-request.  This ensures the
   voucher is fresh.  See Section 5.2.

2.6.2.  Infinite Lifetime of IDevID

   Long-lived pledge certificates "SHOULD be assigned the
   GeneralizedTime value of 99991231235959Z" for the notAfter field as
   explained in [RFC5280].

   Some deployed IDevID management systems are not compliant with the
   802.1AR requirement for infinite lifetimes and are put in typical <=
   3 year certificate lifetimes.  Registrars SHOULD be configurable on a
   per-manufacturer basis to ignore pledge lifetimes when the pledge
   does not follow the recommendations in [RFC5280].

2.7.  Cloud Registrar

   There exist operationally open networks wherein devices gain
   unauthenticated access to the Internet at large.  In these use cases,
   the management domain for the device needs to be discovered within
   the larger Internet.  The case where a device can boot and get access
   to a larger Internet is less likely within the ANIMA ACP scope but
   may be more important in the future.  In the ANIMA ACP scope, new
   devices will be quarantined behind a Join Proxy.

   Additionally, there are some greenfield situations involving an
   entirely new installation where a device may have some kind of
   management uplink that it can use (such as via a 3G network, for
   instance).  In such a future situation, the device might use this
   management interface to learn that it should configure itself to
   become the local registrar.

   In order to support these scenarios, the pledge MAY contact a well-
   known URI of a cloud registrar if a local registrar cannot be
   discovered or if the pledge's target use cases do not include a local
   registrar.

   If the pledge uses a well-known URI for contacting a cloud registrar,
   a manufacturer-assigned Implicit Trust Anchor database (see
   [RFC7030]) MUST be used to authenticate that service as described in
   [RFC6125].  The use of a DNS-ID for validation is appropriate, and it
   may include wildcard components on the left-mode side.  This is
   consistent with the human-user configuration of an EST server URI in
   [RFC7030], which also depends on [RFC6125].

2.8.  Determining the MASA to Contact

   The registrar needs to be able to contact a MASA that is trusted by
   the pledge in order to obtain vouchers.

   The device's IDevID will normally contain the MASA URL as detailed in
   Section 2.3.  This is the RECOMMENDED mechanism.

   In some cases, it can be operationally difficult to ensure the
   necessary X.509 extensions are in the pledge's IDevID due to the
   difficulty of aligning current pledge manufacturing with software
   releases and development; thus, as a final fallback, the registrar
   MAY be manually configured or distributed with a MASA URL for each
   manufacturer.  Note that the registrar can only select the configured
   MASA URL based on the trust anchor -- so manufacturers can only
   leverage this approach if they ensure a single MASA URL works for all
   pledges associated with each trust anchor.

3.  Voucher-Request Artifact

   Voucher-requests are how vouchers are requested.  The semantics of
   the voucher-request are described below, in the YANG module.

   A pledge forms the "pledge voucher-request", signs it with its
   IDevID, and submits it to the registrar.

   In turn, the registrar forms the "registrar voucher-request", signs
   it with its registrar key pair, and submits it to the MASA.

   The "proximity-registrar-cert" leaf is used in the pledge voucher-
   requests.  This provides a method for the pledge to assert the
   registrar's proximity.

   This network proximity results from the following properties in the
   ACP context: the pledge is connected to the Join Proxy (Section 4)
   using a link-local IPv6 connection.  While the Join Proxy does not
   participate in any meaningful sense in the cryptography of the TLS
   connection (such as via a Channel Binding), the registrar can observe
   that the connection is via the private ACP (ULA) address of the Join
   Proxy, and it cannot come from outside the ACP.  The pledge must
   therefore be at most one IPv6 link-local hop away from an existing
   node on the ACP.

   Other users of BRSKI will need to define other kinds of assertions if
   the network proximity described above does not match their needs.

   The "prior-signed-voucher-request" leaf is used in registrar voucher-
   requests.  If present, it is the signed pledge voucher-request
   artifact.  This provides a method for the registrar to forward the
   pledge's signed request to the MASA.  This completes transmission of
   the signed proximity-registrar-cert leaf.

   Unless otherwise signaled (outside the voucher-request artifact), the
   signing structure is as defined for vouchers; see [RFC8366].

3.1.  Nonceless Voucher-Requests

   A registrar MAY also retrieve nonceless vouchers by sending nonceless
   voucher-requests to the MASA in order to obtain vouchers for use when
   the registrar does not have connectivity to the MASA.  No prior-
   signed-voucher-request leaf would be included.  The registrar will
   also need to know the serial number of the pledge.  This document
   does not provide a mechanism for the registrar to learn that in an
   automated fashion.  Typically, this will be done via the scanning of
   a bar code or QR code on packaging, or via some sales channel
   integration.

3.2.  Tree Diagram

   The following tree diagram illustrates a high-level view of a
   voucher-request document.  The voucher-request builds upon the
   voucher artifact described in [RFC8366].  The tree diagram is
   described in [RFC8340].  Each node in the diagram is fully described
   by the YANG module in Section 3.4.  Please review the YANG module for
   a detailed description of the voucher-request format.

   module: ietf-voucher-request

    grouping voucher-request-grouping
     +-- voucher
        +-- created-on?                      yang:date-and-time
        +-- expires-on?                      yang:date-and-time
        +-- assertion?                       enumeration
        +-- serial-number                    string
        +-- idevid-issuer?                   binary
        +-- pinned-domain-cert?              binary
        +-- domain-cert-revocation-checks?   boolean
        +-- nonce?                           binary
        +-- last-renewal-date?               yang:date-and-time
        +-- prior-signed-voucher-request?    binary
        +-- proximity-registrar-cert?        binary

             Figure 5: YANG Tree Diagram for a Voucher-Request

3.3.  Examples

   This section provides voucher-request examples for illustration
   purposes.  These examples show JSON prior to CMS wrapping.  JSON
   encoding rules specify that any binary content be base64 encoded
   ([RFC4648], Section 4).  The contents of the (base64) encoded
   certificates have been elided to save space.  For detailed examples,
   see Appendix C.2.  These examples conform to the encoding rules
   defined in [RFC7951].

   Example (1):  The following example illustrates a pledge voucher-
                 request.  The assertion leaf is indicated as
                 "proximity", and the registrar's TLS server certificate
                 is included in the proximity-registrar-cert leaf.  See
                 Section 5.2.

   {
       "ietf-voucher-request:voucher": {
           "assertion": "proximity",
           "nonce": "62a2e7693d82fcda2624de58fb6722e5",
           "serial-number" : "JADA123456789",
           "created-on": "2017-01-01T00:00:00.000Z",
           "proximity-registrar-cert": "base64encodedvalue=="
       }
   }

        Figure 6: JSON Representation of an Example Voucher-Request

   Example (2):  The following example illustrates a registrar voucher-
                 request.  The prior-signed-voucher-request leaf is
                 populated with the pledge's voucher-request (such as
                 the prior example).  The pledge's voucher-request is a
                 binary CMS-signed object.  In the JSON encoding used
                 here, it must be base64 encoded.  The nonce and
                 assertion have been carried forward from the pledge
                 request to the registrar request.  The serial-number is
                 extracted from the pledge's Client Certificate from the
                 TLS connection.  See Section 5.5.

   {
       "ietf-voucher-request:voucher": {
           "assertion" : "proximity",
           "nonce": "62a2e7693d82fcda2624de58fb6722e5",
           "created-on": "2017-01-01T00:00:02.000Z",
           "idevid-issuer": "base64encodedvalue==",
           "serial-number": "JADA123456789",
           "prior-signed-voucher-request": "base64encodedvalue=="
       }
   }

     Figure 7: JSON Representation of an Example Prior-Signed Voucher-
                                  Request

   Example (3):  The following example illustrates a registrar voucher-
                 request.  The prior-signed-voucher-request leaf is not
                 populated with the pledge's voucher-request nor is the
                 nonce leaf.  This form might be used by a registrar
                 requesting a voucher when the pledge cannot communicate
                 with the registrar (such as when it is powered down or
                 still in packaging) and therefore cannot submit a
                 nonce.  This scenario is most useful when the registrar
                 is aware that it will not be able to reach the MASA
                 during deployment.  See Section 5.5.

   {
       "ietf-voucher-request:voucher": {
           "created-on":    "2017-01-01T00:00:02.000Z",
           "idevid-issuer": "base64encodedvalue==",
           "serial-number": "JADA123456789"
       }
   }

        Figure 8: JSON Representation of an Offline Voucher-Request

3.4.  YANG Module

   Following is a YANG module [RFC7950] that formally extends a voucher
   [RFC8366] into a voucher-request.  This YANG module references
   [ITU.X690].

   <CODE BEGINS> file "ietf-voucher-request@2021-05-20.yang"
   module ietf-voucher-request {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-voucher-request";
     prefix vcr;

     import ietf-restconf {
       prefix rc;
       description
         "This import statement is only present to access
          the yang-data extension defined in RFC 8040.";
       reference
         "RFC 8040: RESTCONF Protocol";
     }
     import ietf-voucher {
       prefix vch;
       description
         "This module defines the format for a voucher,
          which is produced by a pledge's manufacturer or
          delegate (MASA) to securely assign a pledge to
          an 'owner', so that the pledge may establish a secure
          connection to the owner's network infrastructure.";
       reference
         "RFC 8366: A Voucher Artifact for
          Bootstrapping Protocols";
     }

     organization
       "IETF ANIMA Working Group";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/anima/>
        WG List:  <mailto:anima@ietf.org>
        Author:   Kent Watsen
                  <mailto:kent+ietf@watsen.net>
        Author:   Michael H. Behringer
                  <mailto:Michael.H.Behringer@gmail.com>
        Author:   Toerless Eckert
                  <mailto:tte+ietf@cs.fau.de>
        Author:   Max Pritikin
                  <mailto:pritikin@cisco.com>
        Author:   Michael Richardson
                  <mailto:mcr+ietf@sandelman.ca>";
     description
       "This module defines the format for a voucher-request.
        It is a superset of the voucher itself.
        It provides content to the MASA for consideration
        during a voucher-request.

        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
        NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
        'MAY', and 'OPTIONAL' in this document are to be interpreted as
        described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
        they appear in all capitals, as shown here.

        Copyright (c) 2021 IETF Trust and the persons identified as
        authors of the code. All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Simplified BSD License
        set forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC 8995; see the
        RFC itself for full legal notices.";

     revision 2021-05-20 {
       description
         "Initial version";
       reference
         "RFC 8995: Bootstrapping Remote Secure Key Infrastructure
          (BRSKI)";
     }

     // Top-level statement
     rc:yang-data voucher-request-artifact {
       uses voucher-request-grouping;
     }

     // Grouping defined for future usage

     grouping voucher-request-grouping {
       description
         "Grouping to allow reuse/extensions in future work.";
       uses vch:voucher-artifact-grouping {
         refine "voucher/created-on" {
           mandatory false;
         }
         refine "voucher/pinned-domain-cert" {
           mandatory false;
           description
             "A pinned-domain-cert field is not valid in a
              voucher-request, and any occurrence MUST be ignored.";
         }
         refine "voucher/last-renewal-date" {
           description
             "A last-renewal-date field is not valid in a
              voucher-request, and any occurrence MUST be ignored.";
         }
         refine "voucher/domain-cert-revocation-checks" {
           description
             "The domain-cert-revocation-checks field is not valid in a
              voucher-request, and any occurrence MUST be ignored.";
         }
         refine "voucher/assertion" {
           mandatory false;
           description
             "Any assertion included in registrar voucher-requests
              SHOULD be ignored by the MASA.";
         }
         augment "voucher" {
           description
             "Adds leaf nodes appropriate for requesting vouchers.";
           leaf prior-signed-voucher-request {
             type binary;
             description
               "If it is necessary to change a voucher, or re-sign and
                forward a voucher that was previously provided along a
                protocol path, then the previously signed voucher SHOULD
                be included in this field.

                For example, a pledge might sign a voucher-request
                with a proximity-registrar-cert, and the registrar
                then includes it as the prior-signed-voucher-request
                field.  This is a simple mechanism for a chain of
                trusted parties to change a voucher-request, while
                maintaining the prior signature information.

                The registrar and MASA MAY examine the prior-signed
                voucher information for the
                purposes of policy decisions.  For example, this
                information could be useful to a MASA to determine
                that both the pledge and registrar agree on proximity
                assertions.  The MASA SHOULD remove all
                prior-signed-voucher-request information when
                signing a voucher for imprinting so as to minimize
                the final voucher size.";
           }
           leaf proximity-registrar-cert {
             type binary;
             description
               "An X.509 v3 certificate structure, as specified by
                RFC 5280, Section 4, encoded using the ASN.1
                distinguished encoding rules (DER), as specified
                in ITU X.690.

                The first certificate in the registrar TLS server
                certificate_list sequence (the end-entity TLS
                certificate; see RFC 8446) presented by the registrar
                to the pledge.  This MUST be populated in a pledge's
                voucher-request when a proximity assertion is
                requested.";
             reference
               "ITU X.690: Information Technology - ASN.1 encoding
                rules: Specification of Basic Encoding Rules (BER),
                Canonical Encoding Rules (CER) and Distinguished
                Encoding Rules (DER)
                RFC 5280: Internet X.509 Public Key Infrastructure
                Certificate and Certificate Revocation List (CRL)
                Profile
                RFC 8446: The Transport Layer Security (TLS)
                Protocol Version 1.3";
           }
         }
       }
     }
   }
   <CODE ENDS>

                 Figure 9: YANG Module for Voucher-Request

4.  Proxying Details (Pledge -- Proxy -- Registrar)

   This section is normative for uses with an ANIMA ACP.  The use of the
   GRASP mechanism is part of the ACP.  Other users of BRSKI will need
   to define an equivalent proxy mechanism and an equivalent mechanism
   to configure the proxy.

   The role of the proxy is to facilitate communications.  The proxy
   forwards packets between the pledge and a registrar that has been
   provisioned to the proxy via full GRASP ACP discovery.

   This section defines a stateful proxy mechanism that is referred to
   as a "circuit" proxy.  This is a form of Application Level Gateway
   (see [RFC2663], Section 2.9).

   The proxy does not terminate the TLS handshake: it passes streams of
   bytes onward without examination.  A proxy MUST NOT assume any
   specific TLS version.  Please see [RFC8446], Section 9.3 for details
   on TLS invariants.

   A registrar can directly provide the proxy announcements described
   below, in which case the announced port can point directly to the
   registrar itself.  In this scenario, the pledge is unaware that there
   is no proxying occurring.  This is useful for registrars that are
   servicing pledges on directly connected networks.

   As a result of the proxy discovery process in Section 4.1.1, the port
   number exposed by the proxy does not need to be well known or require
   an IANA allocation.

   During the discovery of the registrar by the Join Proxy, the Join
   Proxy will also learn which kinds of proxy mechanisms are available.
   This will allow the Join Proxy to use the lowest impact mechanism
   that the Join Proxy and registrar have in common.

   In order to permit the proxy functionality to be implemented on the
   maximum variety of devices, the chosen mechanism should use the
   minimum amount of state on the proxy device.  While many devices in
   the ANIMA target space will be rather large routers, the proxy
   function is likely to be implemented in the control-plane CPU of such
   a device, with available capabilities for the proxy function similar
   to many class 2 IoT devices.

   The document [ANIMA-STATE] provides a more extensive analysis and
   background of the alternative proxy methods.

4.1.  Pledge Discovery of Proxy

   The result of discovery is a logical communication with a registrar,
   through a proxy.  The proxy is transparent to the pledge.  The
   communication between the pledge and Join Proxy is over IPv6 link-
   local addresses.

   To discover the proxy, the pledge performs the following actions:

   1.  MUST: Obtain a local address using IPv6 methods as described in
       "IPv6 Stateless Address Autoconfiguration" [RFC4862].  Use of
       temporary addresses [RFC8981] is encouraged.  To limit pervasive
       monitoring [RFC7258], a new temporary address MAY use a short
       lifetime (that is, set TEMP_PREFERRED_LIFETIME to be short).
       Pledges will generally prefer use of IPv6 link-local addresses,
       and discovery of the proxy will be by link-local mechanisms.
       IPv4 methods are described in Appendix A.

   2.  MUST: Listen for GRASP M_FLOOD [RFC8990] announcements of the
       objective: "AN_Proxy".  See Section 4.1.1 for the details of the
       objective.  The pledge MAY listen concurrently for other sources
       of information; see Appendix B.

   Once a proxy is discovered, the pledge communicates with a registrar
   through the proxy using the bootstrapping protocol defined in
   Section 5.

   While the GRASP M_FLOOD mechanism is passive for the pledge, the non-
   normative other methods (mDNS and IPv4 methods) described in
   Appendix B are active.  The pledge SHOULD run those methods in
   parallel with listening for the M_FLOOD.  The active methods SHOULD
   back off by doubling to a maximum of one hour to avoid overloading
   the network with discovery attempts.  Detection of physical link
   status change (Ethernet carrier, for instance) SHOULD reset the back-
   off timers.

   The pledge could discover more than one proxy on a given physical
   interface.  The pledge can have a multitude of physical interfaces as
   well: a Layer 2/3 Ethernet switch may have hundreds of physical
   ports.

   Each possible proxy offer SHOULD be attempted up to the point where a
   valid voucher is received: while there are many ways in which the
   attempt may fail, it does not succeed until the voucher has been
   validated.

   The connection attempts via a single proxy SHOULD exponentially back
   off to a maximum of one hour to avoid overloading the network
   infrastructure.  The back-off timer for each MUST be independent of
   other connection attempts.

   Connection attempts SHOULD be run in parallel to avoid head-of-queue
   problems wherein an attacker running a fake proxy or registrar could
   intentionally perform protocol actions slowly.  Connection attempts
   to different proxies SHOULD be sent with an interval of 3 to 5s.  The
   pledge SHOULD continue to listen for additional GRASP M_FLOOD
   messages during the connection attempts.

   Each connection attempt through a distinct Join Proxy MUST have a
   unique nonce in the voucher-request.

   Once a connection to a registrar is established (e.g., establishment
   of a TLS session key), there are expectations of more timely
   responses; see Section 5.2.

   Once all discovered services are attempted (assuming that none
   succeeded), the device MUST return to listening for GRASP M_FLOOD.
   It SHOULD periodically retry any manufacturer-specific mechanisms.
   The pledge MAY prioritize selection order as appropriate for the
   anticipated environment.

4.1.1.  Proxy GRASP Announcements

   A proxy uses the DULL GRASP M_FLOOD mechanism to announce itself.
   This announcement can be within the same message as the ACP
   announcement detailed in [RFC8994].

   The formal Concise Data Definition Language (CDDL) [RFC8610]
   definition is:

   <CODE BEGINS> file "proxygrasp.cddl"
   flood-message = [M_FLOOD, session-id, initiator, ttl,
                    +[objective, (locator-option / [])]]

   objective = ["AN_Proxy", objective-flags, loop-count,
                                          objective-value]

   ttl             = 180000     ; 180,000 ms (3 minutes)
   initiator = ACP address to contact registrar
   objective-flags   = sync-only  ; as in the GRASP spec
   sync-only         =  4         ; M_FLOOD only requires
                                  ; synchronization
   loop-count        =  1         ; one hop only
   objective-value   =  any       ; none

   locator-option    = [ O_IPv6_LOCATOR, ipv6-address,
                       transport-proto, port-number ]
   ipv6-address      = the v6 LL of the Proxy
   $transport-proto /= IPPROTO_TCP   ; note that this can be any value
                                    ; from the IANA protocol registry,
                                    ; as per RFC 8990, Section 2.9.5.1,
                                    ; Note 3.
   port-number      = selected by Proxy
   <CODE ENDS>

           Figure 10: CDDL Definition of Proxy Discovery Message

   Here is an example M_FLOOD announcing a proxy at fe80::1, on TCP port
   4443.

 [M_FLOOD, 12340815, h'fe800000000000000000000000000001', 180000,
             [["AN_Proxy", 4, 1, ""],
              [O_IPv6_LOCATOR,
               h'fe800000000000000000000000000001', IPPROTO_TCP, 4443]]]

             Figure 11: Example of Proxy Discovery Message

   On a small network, the registrar MAY include the GRASP M_FLOOD
   announcements to locally connected networks.

   The $transport-proto above indicates the method that the pledge-
   proxy-registrar will use.  The TCP method described here is
   mandatory, and other proxy methods, such as CoAP methods not defined
   in this document, are optional.  Other methods MUST NOT be enabled
   unless the Join Registrar ASA indicates support for them in its own
   announcement.

4.2.  CoAP Connection to Registrar

   The use of CoAP to connect from pledge to registrar is out of scope
   for this document and is described in future work.  See
   [ANIMA-CONSTRAINED-VOUCHER].

4.3.  Proxy Discovery and Communication of Registrar

   The registrar SHOULD announce itself so that proxies can find it and
   determine what kind of connections can be terminated.

   The registrar announces itself using GRASP M_FLOOD messages, with the
   "AN_join_registrar" objective, within the ACP instance.  A registrar
   may announce any convenient port number, including use of stock port
   443.  ANI proxies MUST support GRASP discovery of registrars.

   The M_FLOOD is formatted as follows:

 [M_FLOOD, 51804321, h'fda379a6f6ee00000200000064000001', 180000,
             [["AN_join_registrar", 4, 255, "EST-TLS"],
              [O_IPv6_LOCATOR,
               h'fda379a6f6ee00000200000064000001', IPPROTO_TCP, 8443]]]

       Figure 12: An Example of a Registrar Announcement Message

   The formal CDDL definition is:

   <CODE BEGINS> file "jrcgrasp.cddl"
   flood-message = [M_FLOOD, session-id, initiator, ttl,
                    +[objective, (locator-option / [])]]

   objective = ["AN_join_registrar", objective-flags, loop-count,
                                          objective-value]

   initiator = ACP address to contact registrar
   objective-flags = sync-only  ; as in the GRASP spec
   sync-only =  4               ; M_FLOOD only requires
                                ; synchronization
   loop-count      = 255        ; mandatory maximum
   objective-value = text       ; name of the (list of) supported
                                ; protocols: "EST-TLS" for RFC 7030.
   <CODE ENDS>

       Figure 13: CDDL Definition for Registrar Announcement Message

   The M_FLOOD message MUST be sent periodically.  The default period
   SHOULD be 60 seconds, and the value SHOULD be operator configurable
   but SHOULD NOT be smaller than 60 seconds.  The frequency of sending
   MUST be such that the aggregate amount of periodic M_FLOODs from all
   flooding sources causes only negligible traffic across the ACP.

   Here are some examples of locators for illustrative purposes.  Only
   the first one ($transport-protocol = 6, TCP) is defined in this
   document and is mandatory to implement.

   locator1  = [O_IPv6_LOCATOR, fd45:1345::6789, 6,  443]
   locator2  = [O_IPv6_LOCATOR, fd45:1345::6789, 17, 5683]
   locator3  = [O_IPv6_LOCATOR, fe80::1234, 41, nil]

   A protocol of 6 indicates that TCP proxying on the indicated port is
   desired.

   Registrars MUST announce the set of protocols that they support, and
   they MUST support TCP traffic.

   Registrars MUST accept HTTPS/EST traffic on the TCP ports indicated.

   Registrars MUST support the ANI TLS Circuit Proxy and therefore BRSKI
   across HTTPS/TLS native across the ACP.

   In the ANI, the ACP-secured instance of GRASP [RFC8990] MUST be used
   for discovery of ANI registrar ACP addresses and ports by ANI
   proxies.  Therefore, the TCP leg of the proxy connection between the
   ANI proxy and ANI registrar also runs across the ACP.

5.  Protocol Details (Pledge -- Registrar -- MASA)

   The pledge MUST initiate BRSKI after boot if it is unconfigured.  The
   pledge MUST NOT automatically initiate BRSKI if it has been
   configured or is in the process of being configured.

   BRSKI is described as extensions to EST [RFC7030].  The goal of these
   extensions is to reduce the number of TLS connections and crypto
   operations required on the pledge.  The registrar implements the
   BRSKI REST interface within the "/.well-known/brski" URI tree and
   implements the existing EST URIs as described in EST [RFC7030],
   Section 3.2.2.  The communication channel between the pledge and the
   registrar is referred to as "BRSKI-EST" (see Figure 1).

   The communication channel between the registrar and MASA is a new
   communication channel, similar to EST, within the newly registered
   "/.well-known/brski" tree.  For clarity, this channel is referred to
   as "BRSKI-MASA" (see Figure 1).

   The MASA URI is "https://" authority "/.well-known/brski".

   BRSKI uses existing CMS message formats for existing EST operations.
   BRSKI uses JSON [RFC8259] for all new operations defined here and for
   voucher formats.  In all places where a binary value must be carried
   in a JSON string, a base64 format ([RFC4648], Section 4) is to be
   used, as per [RFC7951], Section 6.6.

   While EST ([RFC7030], Section 3.2) does not insist upon use of HTTP
   persistent connections ([RFC7230], Section 6.3), BRSKI-EST
   connections SHOULD use persistent connections.  The intention of this
   guidance is to ensure the provisional TLS state occurs only once, and
   that the subsequent resolution of the provision state is not subject
   to a Man-in-the-Middle (MITM) attack during a critical phase.

   If non-persistent connections are used, then both the pledge and the
   registrar MUST remember the certificates that have been seen and also
   sent for the first connection.  They MUST check each subsequent
   connection for the same certificates, and each end MUST use the same
   certificates as well.  This places a difficult restriction on rolling
   certificates on the registrar.

   Summarized automation extensions for the BRSKI-EST flow are:

   *  The pledge either attempts concurrent connections via each
      discovered proxy or times out quickly and tries connections in
      series, as explained at the end of Section 5.1.

   *  The pledge provisionally accepts the registrar certificate during
      the TLS handshake as detailed in Section 5.1.

   *  The pledge requests a voucher using the new REST calls described
      below.  This voucher is then validated.

   *  The pledge completes authentication of the server certificate as
      detailed in Section 5.6.1.  This moves the BRSKI-EST TLS
      connection out of the provisional state.

   *  Mandatory bootstrap steps conclude with voucher status telemetry
      (see Section 5.7).

   The BRSKI-EST TLS connection can now be used for EST enrollment.

   The extensions for a registrar (equivalent to an EST server) are:

   *  Client authentication is automated using IDevID as per the EST
      certificate-based client authentication.  The subject field's DN
      encoding MUST include the "serialNumber" attribute with the
      device's unique serial number as explained in Section 2.3.1.

   *  The registrar requests and validates the voucher from the MASA.

   *  The registrar forwards the voucher to the pledge when requested.

   *  The registrar performs log verifications (described in
      Section 5.8.3) in addition to local authorization checks before
      accepting optional pledge device enrollment requests.

5.1.  BRSKI-EST TLS Establishment Details

   The pledge establishes the TLS connection with the registrar through
   the Circuit Proxy (see Section 4), but the TLS handshake is with the
   registrar.  The BRSKI-EST pledge is the TLS client, and the BRSKI-EST
   registrar is the TLS server.  All security associations established
   are between the pledge and the registrar regardless of proxy
   operations.

   Use of TLS 1.3 (or newer) is encouraged.  TLS 1.2 or newer is
   REQUIRED on the pledge side.  TLS 1.3 (or newer) SHOULD be available
   on the registrar server interface, and the registrar client
   interface, but TLS 1.2 MAY be used.  TLS 1.3 (or newer) SHOULD be
   available on the MASA server interface, but TLS 1.2 MAY be used.

   Establishment of the BRSKI-EST TLS connection is as specified in
   "Bootstrap Distribution of CA Certificates" (Section 4.1.1) of
   [RFC7030], wherein the client is authenticated with the IDevID
   certificate, and the EST server (the registrar) is provisionally
   authenticated with an unverified server certificate.  Configuration
   or distribution of the trust anchor database used for validating the
   IDevID certificate is out of scope of this specification.  Note that
   the trust anchors in / excluded from the database will affect which
   manufacturers' devices are acceptable to the registrar as pledges and
   can also be used to limit the set of MASAs that are trusted for
   enrollment.

   The signature in the certificate MUST be validated even if a signing
   key cannot (yet) be validated.  The certificate (or chain) MUST be
   retained for later validation.

   A self-signed certificate for the registrar is acceptable as the
   voucher can validate it upon successful enrollment.

   The pledge performs input validation of all data received until a
   voucher is verified as specified in Section 5.6.1 and the TLS
   connection leaves the provisional state.  Until these operations are
   complete, the pledge could be communicating with an attacker.

   The pledge code needs to be written with the assumption that all data
   is being transmitted at this point to an unauthenticated peer, and
   that received data, while inside a TLS connection, MUST be considered
   untrusted.  This particularly applies to HTTP headers and CMS
   structures that make up the voucher.

   A pledge that can connect to multiple registrars concurrently SHOULD
   do so.  Some devices may be unable to do so for lack of threading, or
   resource issues.  Concurrent connections defeat attempts by a
   malicious proxy from causing a TCP Slowloris-like attack (see
   [slowloris]).

   A pledge that cannot maintain as many connections as there are
   eligible proxies will need to rotate among the various choices,
   terminating connections that do not appear to be making progress.  If
   no connection is making progress after 5 seconds, then the pledge
   SHOULD drop the oldest connection and go on to a different proxy: the
   proxy that has been communicated with least recently.  If there were
   no other proxies discovered, the pledge MAY continue to wait, as long
   as it is concurrently listening for new proxy announcements.

5.2.  Pledge Requests Voucher from the Registrar

   When the pledge bootstraps, it makes a request for a voucher from a
   registrar.

   This is done with an HTTPS POST using the operation path value of
   "/.well-known/brski/requestvoucher".

   The pledge voucher-request Content-Type is as follows.

   application/voucher-cms+json:  [RFC8366] defines a "YANG-defined JSON
      document that has been signed using a Cryptographic Message Syntax
      (CMS) structure", and the voucher-request described in Section 3
      is created in the same way.  The media type is the same as defined
      in [RFC8366].  This is also used for the pledge voucher-request.
      The pledge MUST sign the request using the credentials in
      Section 2.3.

   Registrar implementations SHOULD anticipate future media types but,
   of course, will simply fail the request if those types are not yet
   known.

   The pledge SHOULD include an "Accept" header field (see [RFC7231],
   Section 5.3.2) indicating the acceptable media type for the voucher
   response.  The "application/voucher-cms+json" media type is defined
   in [RFC8366], but constrained voucher formats are expected in the
   future.  Registrars and MASA are expected to be flexible in what they
   accept.

   The pledge populates the voucher-request fields as follows:

   created-on:  Pledges that have a real-time clock are RECOMMENDED to
      populate this field with the current date and time in yang:date-
      and-time format.  This provides additional information to the
      MASA.  Pledges that have no real-time clocks MAY omit this field.

   nonce:  The pledge voucher-request MUST contain a cryptographically
      strong random or pseudo-random number nonce (see [RFC4086],
      Section 6.2).  As the nonce is usually generated very early in the
      boot sequence, there is a concern that the same nonce might be
      generated across multiple boots, or after a factory reset.
      Different nonces MUST be generated for each bootstrapping attempt,
      whether in series or concurrently.  The freshness of this nonce
      mitigates against the lack of a real-time clock as explained in
      Section 2.6.1.

   assertion:  The pledge indicates support for the mechanism described
      in this document, by putting the value "proximity" in the voucher-
      request, and MUST include the proximity-registrar-cert field
      (below).

   proximity-registrar-cert:  In a pledge voucher-request, this is the
      first certificate in the TLS server "certificate_list" sequence
      (see [RFC8446], Section 4.4.2) presented by the registrar to the
      pledge.  That is, it is the end-entity certificate.  This MUST be
      populated in a pledge voucher-request.

   serial-number:  The serial number of the pledge is included in the
      voucher-request from the pledge.  This value is included as a
      sanity check only, but it is not to be forwarded by the registrar
      as described in Section 5.5.

   All other fields MAY be omitted in the pledge voucher-request.

   See an example JSON payload of a pledge voucher-request in
   Section 3.3, Example 1.

   The registrar confirms that the assertion is "proximity" and that
   pinned proximity-registrar-cert is the registrar's certificate.  If
   this validation fails, then there is an on-path attacker (MITM), and
   the connection MUST be closed after the returning of an HTTP 401
   error code.

5.3.  Registrar Authorization of Pledge

   In a fully automated network, all devices must be securely identified
   and authorized to join the domain.

   A registrar accepts or declines a request to join the domain, based
   on the authenticated identity presented.  For different networks,
   examples of automated acceptance may include the allowance of:

   *  any device of a specific type (as determined by the X.509 IDevID),

   *  any device from a specific vendor (as determined by the X.509
      IDevID),

   *  a specific device from a vendor (as determined by the X.509
      IDevID) against a domain acceptlist.  (The mechanism for checking
      a shared acceptlist potentially used by multiple registrars is out
      of scope.)

   If validation fails, the registrar SHOULD respond with the HTTP 404
   error code.  If the voucher-request is in an unknown format, then an
   HTTP 406 error code is more appropriate.  A situation that could be
   resolved with administrative action (such as adding a vendor to an
   acceptlist) MAY be responded to with a 403 HTTP error code.

   If authorization is successful, the registrar obtains a voucher from
   the MASA service (see Section 5.5) and returns that MASA-signed
   voucher to the pledge as described in Section 5.6.

5.4.  BRSKI-MASA TLS Establishment Details

   The BRSKI-MASA TLS connection is a "normal" TLS connection
   appropriate for HTTPS REST interfaces.  The registrar initiates the
   connection and uses the MASA URL that is obtained as described in
   Section 2.8.  The mechanisms in [RFC6125] SHOULD be used in
   authentication of the MASA using a DNS-ID that matches that which is
   found in the IDevID.  Registrars MAY include a mechanism to override
   the MASA URL on a manufacturer-by-manufacturer basis, and within that
   override, it is appropriate to provide alternate anchors.  This will
   typically be used by some vendors to establish explicit (or private)
   trust anchors for validating their MASA that is part of a sales
   channel integration.

   Use of TLS 1.3 (or newer) is encouraged.  TLS 1.2 or newer is
   REQUIRED.  TLS 1.3 (or newer) SHOULD be available.

   As described in [RFC7030], the MASA and the registrars SHOULD be
   prepared to support TLS Client Certificate authentication and/or HTTP
   Basic, Digest, or Salted Challenge Response Authentication Mechanism
   (SCRAM) authentication.  This connection MAY also have no client
   authentication at all.

   Registrars SHOULD permit trust anchors to be preconfigured on a per-
   vendor (MASA) basis.  Registrars SHOULD include the ability to
   configure a TLS Client Certificate on a per-MASA basis, or to use no
   Client Certificate.  Registrars SHOULD also permit HTTP Basic and
   Digest authentication to be configured.

   The authentication of the BRSKI-MASA connection does not change the
   voucher-request process, as voucher-requests are already signed by
   the registrar.  Instead, this authentication provides access control
   to the audit-log as described in Section 5.8.

   Implementers are advised that contacting the MASA establishes a
   secured API connection with a web service, and that there are a
   number of authentication models being explored within the industry.
   Registrars are RECOMMENDED to fail gracefully and generate useful
   administrative notifications or logs in the advent of unexpected HTTP
   401 (Unauthorized) responses from the MASA.

5.4.1.  MASA Authentication of Customer Registrar

   Providing per-customer options requires the customer's registrar to
   be uniquely identified.  This can be done by any stateless method
   that HTTPS supports such as HTTP Basic or Digest authentication (that
   is using a password), but the use of TLS Client Certificate
   authentication is RECOMMENDED.

   Stateful methods involving API tokens, or HTTP Cookies, are not
   recommended.

   It is expected that the setup and configuration of per-customer
   Client Certificates is done as part of a sales ordering process.

   The use of public PKI (i.e., WebPKI) end-entity certificates to
   identify the registrar is reasonable, and if done universally, this
   would permit a MASA to identify a customer's registrar simply by a
   Fully Qualified Domain Name (FQDN).

   The use of DANE records in DNSSEC-signed zones would also permit use
   of a FQDN to identify customer registrars.

   A third (and simplest, but least flexible) mechanism would be for the
   MASA to simply store the registrar's certificate pinned in a
   database.

   A MASA without any supply-chain integration can simply accept
   registrars without any authentication or on a blind TOFU basis as
   described in Section 7.4.2.

   This document does not make a specific recommendation on how the MASA
   authenticates the registrar as there are likely different tradeoffs
   in different environments and product values.  Even within the ANIMA
   ACP applicability, there is a significant difference between supply-
   chain logistics for $100 CPE devices and $100,000 core routers.

5.5.  Registrar Requests Voucher from MASA

   When a registrar receives a pledge voucher-request, it in turn
   submits a registrar voucher-request to the MASA service via an HTTPS
   interface [RFC7231].

   This is done with an HTTP POST using the operation path value of
   "/.well-known/brski/requestvoucher".

   The voucher media type "application/voucher-cms+json" is defined in
   [RFC8366] and is also used for the registrar voucher-request.  It is
   a JSON document that has been signed using a CMS structure.  The
   registrar MUST sign the registrar voucher-request.

   MASA implementations SHOULD anticipate future media ntypes but, of
   course, will simply fail the request if those types are not yet
   known.

   The voucher-request CMS object includes some number of certificates
   that are input to the MASA as it populates the pinned-domain-cert.
   As [RFC8366] is quite flexible in what may be put into the pinned-
   domain-cert, the MASA needs some signal as to what certificate would
   be effective to populate the field with: it may range from the end-
   entity certificate that the registrar uses to the entire private
   Enterprise CA certificate.  More-specific certificates result in a
   tighter binding of the voucher to the domain, while less-specific
   certificates result in more flexibility in how the domain is
   represented by certificates.

   A registrar that is seeking a nonceless voucher for later offline use
   benefits from a less-specific certificate, as it permits the actual
   key pair used by a future registrar to be determined by the pinned
   CA.

   In some cases, a less-specific certificate, such as a public WebPKI
   CA, could be too open and could permit any entity issued a
   certificate by that authority to assume ownership of a device that
   has a voucher pinned.  Future work may provide a solution to pin both
   a certificate and a name that would reduce such risk of malicious
   ownership assertions.

   The registrar SHOULD request a voucher with the most specificity
   consistent with the mode that it is operating in.  In order to do
   this, when the registrar prepares the CMS structure for the signed
   voucher-request, it SHOULD include only certificates that are a part
   of the chain that it wishes the MASA to pin.  This MAY be as small as
   only the end-entity certificate (with id-kp-cmcRA set) that it uses
   as its TLS server certificate, or it MAY be the entire chain,
   including the domain CA.

   The registrar SHOULD include an "Accept" header field (see [RFC7231],
   Section 5.3.2) indicating the response media types that are
   acceptable.  This list SHOULD be the entire list presented to the
   registrar in the pledge's original request (see Section 5.2), but it
   MAY be a subset.  The MASA is expected to be flexible in what it
   accepts.

   The registrar populates the voucher-request fields as follows:

   created-on:  The registrar SHOULD populate this field with the
      current date and time when the voucher-request is formed.  This
      field provides additional information to the MASA.

   nonce:  This value, if present, is copied from the pledge voucher-
      request.  The registrar voucher-request MAY omit the nonce as per
      Section 3.1.

   serial-number:  The serial number of the pledge the registrar would
      like a voucher for.  The registrar determines this value by
      parsing the authenticated pledge IDevID certificate; see
      Section 2.3.  The registrar MUST verify that the serial-number
      field it parsed matches the serial-number field the pledge
      provided in its voucher-request.  This provides a sanity check
      useful for detecting error conditions and logging.  The registrar
      MUST NOT simply copy the serial-number field from a pledge
      voucher-request as that field is claimed but not certified.

   idevid-issuer:  The Issuer value from the pledge IDevID certificate
      is included to ensure unique interpretation of the serial-number.
      In the case of a nonceless (offline) voucher-request, an
      appropriate value needs to be configured from the same out-of-band
      source as the serial-number.

   prior-signed-voucher-request:  The signed pledge voucher-request
      SHOULD be included in the registrar voucher-request.  The entire
      CMS-signed structure is to be included and base64 encoded for
      transport in the JSON structure.

   A nonceless registrar voucher-request MAY be submitted to the MASA.
   Doing so allows the registrar to request a voucher when the pledge is
   offline, or when the registrar anticipates not being able to connect
   to the MASA while the pledge is being deployed.  Some use cases
   require the registrar to learn the appropriate IDevID serialNumber
   field and appropriate "Accept" header field values from the physical
   device labeling or from the sales channel (which is out of scope for
   this document).

   All other fields MAY be omitted in the registrar voucher-request.

   The proximity-registrar-cert field MUST NOT be present in the
   registrar voucher-request.

   See example JSON payloads of registrar voucher-requests in
   Section 3.3, Examples 2 through 4.

   The MASA verifies that the registrar voucher-request is internally
   consistent but does not necessarily authenticate the registrar
   certificate since the registrar MAY be unknown to the MASA in
   advance.  The MASA performs the actions and validation checks
   described in the following subsections before issuing a voucher.

5.5.1.  MASA Renewal of Expired Vouchers

   As described in [RFC8366], vouchers are normally short lived to avoid
   revocation issues.  If the request is for a previous (expired)
   voucher using the same registrar (that is, a registrar with the same
   domain CA), then the request for a renewed voucher SHOULD be
   automatically authorized.  The MASA has sufficient information to
   determine this by examining the request, the registrar
   authentication, and the existing audit-log.  The issuance of a
   renewed voucher is logged as detailed in Section 5.6.

   To inform the MASA that existing vouchers are not to be renewed, one
   can update or revoke the registrar credentials used to authorize the
   request (see Sections 5.5.4 and 5.5.3).  More flexible methods will
   likely involve sales channel integration and authorizations (details
   are out of scope of this document).

5.5.2.  MASA Pinning of Registrar

   A certificate chain is extracted from the registrar's signed CMS
   container.  This chain may be as short as a single end-entity
   certificate, up to the entire registrar certificate chain, including
   the domain CA certificate, as specified in Section 5.5.

   If the domain's CA is unknown to the MASA, then it is considered a
   temporary trust anchor for the rest of the steps in this section.
   The intention is not to authenticate the message as having come from
   a fully validated origin but to establish the consistency of the
   domain PKI.

   The MASA MAY use the certificate in the chain that is farthest from
   the end-entity certificate of the registrar, as determined by MASA
   policy.  A MASA MAY have a local policy in which it only pins the
   end-entity certificate.  This is consistent with [RFC8366].  Details
   of the policy will typically depend upon the degree of supply-chain
   integration and the mechanism used by the registrar to authenticate.
   Such a policy would also determine how the MASA will respond to a
   request for a nonceless voucher.

5.5.3.  MASA Check of the Voucher-Request Signature

   As described in Section 5.5.2, the MASA has extracted the registrar's
   domain CA.  This is used to validate the CMS signature [RFC5652] on
   the voucher-request.

   Normal PKIX revocation checking is assumed during voucher-request
   signature validation.  This CA certificate MAY have Certificate
   Revocation List (CRL) distribution points or Online Certificate
   Status Protocol (OCSP) information [RFC6960].  If they are present,
   the MASA MUST be able to reach the relevant servers belonging to the
   registrar's domain CA to perform the revocation checks.

   The use of OCSP Stapling is preferred.

5.5.4.  MASA Verification of the Domain Registrar

   The MASA MUST verify that the registrar voucher-request is signed by
   a registrar.  This is confirmed by verifying that the id-kp-cmcRA
   extended key usage extension field (as detailed in EST [RFC7030],
   Section 3.6.1) exists in the certificate of the entity that signed
   the registrar voucher-request.  This verification is only a
   consistency check to ensure that the unauthenticated domain CA
   intended the voucher-request signer to be a registrar.  Performing
   this check provides value to the domain PKI by assuring the domain
   administrator that the MASA service will only respect claims from
   authorized registration authorities of the domain.

   Even when a domain CA is authenticated to the MASA, and there is
   strong sales channel integration to understand who the legitimate
   owner is, the above id-kp-cmcRA check prevents arbitrary end-entity
   certificates (such as an LDevID certificate) from having vouchers
   issued against them.

   Other cases of inappropriate voucher issuance are detected by
   examination of the audit-log.

   If a nonceless voucher-request is submitted, the MASA MUST
   authenticate the registrar either as described in EST (see Sections
   3.2.3 and 3.3.2 of [RFC7030]) or by validating the registrar's
   certificate used to sign the registrar voucher-request using a
   configured trust anchor.  Any of these methods reduce the risk of
   DDoS attacks and provide an authenticated identity as an input to
   sales channel integration and authorizations (details are out of
   scope of this document).

   In the nonced case, validation of the registrar's identity (via TLS
   Client Certificate or HTTP authentication) MAY be omitted if the MASA
   knows that the device policy is to accept audit-only vouchers.

5.5.5.  MASA Verification of the Pledge 'prior-signed-voucher-request'

   The MASA MAY verify that the registrar voucher-request includes the
   prior-signed-voucher-request field.  If so, the prior-signed-voucher-
   request MUST include a proximity-registrar-cert that is consistent
   with the certificate used to sign the registrar voucher-request.
   Additionally, the voucher-request serial-number leaf MUST match the
   pledge serial-number that the MASA extracts from the signing
   certificate of the prior-signed-voucher-request.  The consistency
   check described above entails checking that the proximity-registrar-
   cert Subject Public Key Info (SPKI) Fingerprint exists within the
   registrar voucher-request CMS signature's certificate chain.  This is
   substantially the same as the pin validation described in [RFC7469],
   Section 2.6.

   If these checks succeed, the MASA updates the voucher and audit-log
   assertion leafs with the "proximity" assertion, as defined by
   [RFC8366], Section 5.3.

5.5.6.  MASA Nonce Handling

   The MASA does not verify the nonce itself.  If the registrar voucher-
   request contains a nonce, and the prior-signed-voucher-request
   exists, then the MASA MUST verify that the nonce is consistent.
   (Recall from above that the voucher-request might not contain a
   nonce; see Sections 5.5 and 5.5.4.)

   The MASA populates the audit-log with the nonce that was verified.
   If a nonceless voucher is issued, then the audit-log is to be
   populated with the JSON value "null".

5.6.  MASA and Registrar Voucher Response

   The MASA voucher response to the registrar is forwarded without
   changes to the pledge; therefore, this section applies to both the
   MASA and the registrar.  The HTTP signaling described applies to both
   the MASA and registrar responses.

   When a voucher-request arrives at the registrar, if it has a cached
   response from the MASA for the corresponding registrar voucher-
   request, that cached response can be used according to local policy;
   otherwise, the registrar constructs a new registrar voucher-request
   and sends it to the MASA.

   Registrar evaluation of the voucher itself is purely for transparency
   and audit purposes to further inform log verification (see
   Section 5.8.3); therefore, a registrar could accept future voucher
   formats that are opaque to the registrar.

   If the voucher-request is successful, the server (a MASA responding
   to a registrar or a registrar responding to a pledge) response MUST
   contain an HTTP 200 response code.  The server MUST answer with a
   suitable 4xx or 5xx HTTP [RFC7230] error code when a problem occurs.
   In this case, the response data from the MASA MUST be a plain text
   human-readable (UTF-8) error message containing explanatory
   information describing why the request was rejected.

   The registrar MAY respond with an HTTP 202 ("the request has been
   accepted for processing, but the processing has not been completed")
   as described in EST [RFC7030], Section 4.2.3, wherein the client
   "MUST wait at least the specified "retry-after" time before repeating
   the same request" (also see [RFC7231], Section 6.6.4).  The pledge is
   RECOMMENDED to provide local feedback (blinked LED, etc.) during this
   wait cycle if mechanisms for this are available.  To prevent an
   attacker registrar from significantly delaying bootstrapping, the
   pledge MUST limit the Retry-After time to 60 seconds.  Ideally, the
   pledge would keep track of the appropriate Retry-After header field
   values for any number of outstanding registrars, but this would
   involve a state table on the pledge.  Instead, the pledge MAY ignore
   the exact Retry-After value in favor of a single hard-coded value (a
   registrar that is unable to complete the transaction after the first
   60 seconds has another chance a minute later).  A pledge SHOULD be
   willing to maintain a 202 retry-state for up to 4 days, which is
   longer than a long weekend, after which time the enrollment attempt
   fails, and the pledge returns to Discovery state.  This allows time
   for an alert to get from the registrar to a human operator who can
   make a decision as to whether or not to proceed with the enrollment.

   A pledge that retries a request after receiving a 202 message MUST
   resend the same voucher-request.  It MUST NOT sign a new voucher-
   request each time, and in particular, it MUST NOT change the nonce
   value.

   In order to avoid infinite redirect loops, which a malicious
   registrar might do in order to keep the pledge from discovering the
   correct registrar, the pledge MUST NOT follow more than one
   redirection (3xx code) to another web origin.  EST supports
   redirection but requires user input; this change allows the pledge to
   follow a single redirection without a user interaction.

   A 403 (Forbidden) response is appropriate if the voucher-request is
   not signed correctly or is stale or if the pledge has another
   outstanding voucher that cannot be overridden.

   A 404 (Not Found) response is appropriate when the request is for a
   device that is not known to the MASA.

   A 406 (Not Acceptable) response is appropriate if a voucher of the
   desired type or that uses the desired algorithms (as indicated by the
   "Accept" header fields and algorithms used in the signature) cannot
   be issued as such because the MASA knows the pledge cannot process
   that type.  The registrar SHOULD use this response if it determines
   the pledge is unacceptable due to inventory control, MASA audit-logs,
   or any other reason.

   A 415 (Unsupported Media Type) response is appropriate for a request
   that has a voucher-request or "Accept" value that is not understood.

   The voucher response format is as indicated in the submitted "Accept"
   header fields or based on the MASA's prior understanding of proper
   format for this pledge.  Only the "application/voucher-cms+json"
   media type [RFC8366] is defined at this time.  The syntactic details
   of vouchers are described in detail in [RFC8366].  Figure 14 shows a
   sample of the contents of a voucher.

   {
     "ietf-voucher:voucher": {
       "nonce": "62a2e7693d82fcda2624de58fb6722e5",
       "assertion": "logged",
       "pinned-domain-cert": "base64encodedvalue==",
       "serial-number": "JADA123456789"
     }
   }

                       Figure 14: An Example Voucher

   The MASA populates the voucher fields as follows:

   nonce:  The nonce from the pledge if available.  See Section 5.5.6.

   assertion:  The method used to verify the relationship between the
      pledge and registrar.  See Section 5.5.5.

   pinned-domain-cert:  A certificate; see Section 5.5.2.  This figure
      is illustrative; for an example, see Appendix C.2 where an end-
      entity certificate is used.

   serial-number:  The serial-number as provided in the voucher-request.
      Also see Section 5.5.5.

   domain-cert-revocation-checks:  Set as appropriate for the pledge's
      capabilities and as documented in [RFC8366].  The MASA MAY set
      this field to "false" since setting it to "true" would require
      that revocation information be available to the pledge, and this
      document does not make normative requirements for [RFC6961],
      Section 4.4.2.1 of [RFC8446], or equivalent integrations.

   expires-on:  This is set for nonceless vouchers.  The MASA ensures
      the voucher lifetime is consistent with any revocation or pinned-
      domain-cert consistency checks the pledge might perform.  See
      Section 2.6.1.  There are three times to consider: (a) a
      configured voucher lifetime in the MASA, (b) the expiry time for
      the registrar's certificate, and (c) any CRL lifetime.  The
      expires-on field SHOULD be before the earliest of these three
      values.  Typically, (b) will be some significant time in the
      future, but (c) will typically be short (on the order of a week or
      less).  The RECOMMENDED period for (a) is on the order of 20
      minutes, so it will typically determine the life span of the
      resulting voucher.  20 minutes is sufficient time to reach the
      post-provisional state in the pledge, at which point there is an
      established trust relationship between the pledge and registrar.
      The subsequent operations can take as long as required from that
      point onwards.  The lifetime of the voucher has no impact on the
      life span of the ownership relationship.

   Whenever a voucher is issued, the MASA MUST update the audit-log
   sufficiently to generate the response as described in Section 5.8.1.
   The internal state requirements to maintain the audit-log are out of
   scope.

5.6.1.  Pledge Voucher Verification

   The pledge MUST verify the voucher signature using the manufacturer-
   installed trust anchor(s) associated with the manufacturer's MASA
   (this is likely included in the pledge's firmware).  Management of
   the manufacturer-installed trust anchor(s) is out of scope of this
   document; this protocol does not update this trust anchor(s).

   The pledge MUST verify that the serial-number field of the signed
   voucher matches the pledge's own serial-number.

   The pledge MUST verify the nonce information in the voucher.  If
   present, the nonce in the voucher must match the nonce the pledge
   submitted to the registrar; vouchers with no nonce can also be
   accepted (according to local policy; see Section 7.2).

   The pledge MUST be prepared to parse and fail gracefully from a
   voucher response that does not contain a pinned-domain-cert field.
   Such a thing indicates a failure to enroll in this domain, and the
   pledge MUST attempt joining with other available Join Proxies.

   The pledge MUST be prepared to ignore additional fields that it does
   not recognize.

5.6.2.  Pledge Authentication of Provisional TLS Connection

   Following the process described in [RFC8366], the pledge should
   consider the public key from the pinned-domain-cert as the sole
   temporary trust anchor.

   The pledge then evaluates the TLS server certificate chain that it
   received when the TLS connection was formed using this trust anchor.
   It is possible that the public key in the pinned-domain-cert directly
   matches the public key in the end-entity certificate provided by the
   TLS server.

   If a registrar's credentials cannot be verified using the pinned-
   domain-cert trust anchor from the voucher, then the TLS connection is
   discarded, and the pledge abandons attempts to bootstrap with this
   discovered registrar.  The pledge SHOULD send voucher status
   telemetry (described below) before closing the TLS connection.  The
   pledge MUST attempt to enroll using any other proxies it has found.
   It SHOULD return to the same proxy again after unsuccessful attempts
   with other proxies.  Attempts should be made at repeated intervals
   according to the back-off timer described earlier.  Attempts SHOULD
   be repeated as failure may be the result of a temporary inconsistency
   (an inconsistently rolled registrar key, or some other
   misconfiguration).  The inconsistency could also be the result of an
   active MITM attack on the EST connection.

   The registrar MUST use a certificate that chains to the pinned-
   domain-cert as its TLS server certificate.

   The pledge's PKIX path validation of a registrar certificate's
   validity period information is as described in Section 2.6.1.  Once
   the PKIX path validation is successful, the TLS connection is no
   longer provisional.

   The pinned-domain-cert MAY be installed as a trust anchor for future
   operations such as enrollment (e.g., as recommended per [RFC7030]) or
   trust anchor management or raw protocols that do not need full PKI-
   based key management.  It can be used to authenticate any dynamically
   discovered EST server that contains the id-kp-cmcRA extended key
   usage extension as detailed in EST (see [RFC7030], Section 3.6.1);
   but to reduce system complexity, the pledge SHOULD avoid additional
   discovery operations.  Instead, the pledge SHOULD communicate
   directly with the registrar as the EST server.  The pinned-domain-
   cert is not a complete distribution of the CA certificate response,
   as described in [RFC7030], Section 4.1.3, which is an additional
   justification for the recommendation to proceed with EST key
   management operations.  Once a full CA certificate response is
   obtained, it is more authoritative for the domain than the limited
   pinned-domain-cert response.

5.7.  Pledge BRSKI Status Telemetry

   The domain is expected to provide indications to the system
   administrators concerning device life-cycle status.  To facilitate
   this, it needs telemetry information concerning the device's status.

   The pledge MUST indicate its pledge status regarding the voucher.  It
   does this by sending a status message to the registrar.

   The posted data media type: application/json

   The client sends an HTTP POST to the server at the URI ".well-
   known/brski/voucher_status".

   The format and semantics described below are for version 1.  A
   version field is included to permit significant changes to this
   feedback in the future.  A registrar that receives a status message
   with a version larger than it knows about SHOULD log the contents and
   alert a human.

   The status field indicates if the voucher was acceptable.  Boolean
   values are acceptable, where "true" indicates the voucher was
   acceptable.

   If the voucher was not acceptable, the Reason string indicates why.
   In a failure case, this message may be sent to an unauthenticated,
   potentially malicious registrar; therefore, the Reason string SHOULD
   NOT provide information beneficial to an attacker.  The operational
   benefit of this telemetry information is balanced against the
   operational costs of not recording that a voucher was ignored by a
   client that the registrar expected was going to continue joining the
   domain.

   The reason-context attribute is an arbitrary JSON object (literal
   value or hash of values) that provides additional information
   specific to this pledge.  The contents of this field are not subject
   to standardization.

   The version and status fields MUST be present.  The Reason field
   SHOULD be present whenever the status field is false.  The Reason-
   Context field is optional.  In the case of a SUCCESS, the Reason
   string MAY be omitted.

   The keys to this JSON object are case sensitive and MUST be
   lowercase.  Figure 16 shows an example JSON.

   <CODE BEGINS> file "voucherstatus.cddl"
   voucherstatus-post = {
       "version": uint,
       "status": bool,
       ? "reason": text,
       ? "reason-context" : { $$arbitrary-map }
     }
   }
   <CODE ENDS>

                  Figure 15: CDDL for Voucher Status POST

   {
       "version": 1,
       "status":false,
       "reason":"Informative human-readable message",
       "reason-context": { "additional" : "JSON" }
   }

                    Figure 16: Example Status Telemetry

   The server SHOULD respond with an HTTP 200 but MAY simply fail with
   an HTTP 404 error.  The client ignores any response.  The server
   SHOULD capture this telemetry information within the server logs.

   Additional standard JSON fields in this POST MAY be added; see
   Section 8.5.  A server that sees unknown fields should log them, but
   otherwise ignore them.

5.8.  Registrar Audit-Log Request

   After receiving the pledge status telemetry (see Section 5.7), the
   registrar SHOULD request the MASA audit-log from the MASA service.

   This is done with an HTTP POST using the operation path value of
   "/.well-known/brski/requestauditlog".

   The registrar SHOULD HTTP POST the same registrar voucher-request as
   it did when requesting a voucher (using the same Content-Type).  It
   is posted to the /requestauditlog URI instead.  The idevid-issuer and
   serial-number informs the MASA which log is requested, so the
   appropriate log can be prepared for the response.  Using the same
   media type and message minimizes cryptographic and message
   operations, although it results in additional network traffic.  The
   relying MASA implementation MAY leverage internal state to associate
   this request with the original, and by now already validated,
   voucher-request so as to avoid an extra crypto validation.

   A registrar MAY request logs at future times.  If the registrar
   generates a new request, then the MASA is forced to perform the
   additional cryptographic operations to verify the new request.

   A MASA that receives a request for a device that does not exist, or
   for which the requesting owner was never an owner, returns an HTTP
   404 ("Not found") code.

   It is reasonable for a registrar, that the MASA does not believe to
   be the current owner, to request the audit-log.  There are probably
   reasons for this, which are hard to predict in advance.  For
   instance, such a registrar may not be aware that the device has been
   resold; it may be that the device has been resold inappropriately,
   and this is how the original owner will learn of the occurrence.  It
   is also possible that the device legitimately spends time in two
   different networks.

   Rather than returning the audit-log as a response to the POST (with a
   return code 200), the MASA MAY instead return a 201 ("Created")
   response ([RFC7231], Sections 6.3.2 and 7.1), with the URL to the
   prepared (and idempotent, therefore cachable) audit response in the
   "Location" header field.

   In order to avoid enumeration of device audit-logs, a MASA that
   returns URLs SHOULD take care to make the returned URL unguessable.
   [W3C.capability-urls] provides very good additional guidance.  For
   instance, rather than returning URLs containing a database number
   such as https://example.com/auditlog/1234 or the Extended Unique
   Identifier (EUI) of the device such https://example.com/
   auditlog/10-00-00-11-22-33, the MASA SHOULD return a randomly
   generated value (a "slug" in web parlance).  The value is used to
   find the relevant database entry.

   A MASA that returns a code 200 MAY also include a "Location" header
   for future reference by the registrar.

5.8.1.  MASA Audit-Log Response

   A log data file is returned consisting of all log entries associated
   with the device selected by the IDevID presented in the request.  The
   audit-log may be abridged by removal of old or repeated values as
   explained below.  The returned data is in JSON format [RFC8259], and
   the Content-Type SHOULD be "application/json".

   The following CDDL [RFC8610] explains the structure of the JSON
   format audit-log response:

   <CODE BEGINS> file "auditlog.cddl"
   audit-log-response = {
     "version": uint,
     "events": [ + event ]
     "truncation": {
       ? "nonced duplicates": uint,
       ? "nonceless duplicates": uint,
       ? "arbitrary": uint,
     }
   }

   event = {
     "date": text,
     "domainID": text,
     "nonce": text / null,
     "assertion": "verified" / "logged" / "proximity",
     ? "truncated": uint,
   }
   <CODE ENDS>

                   Figure 17: CDDL for Audit-Log Response

   An example:

   {
     "version":"1",
     "events":[
       {
           "date":"2019-05-15T17:25:55.644-04:00",
           "domainID":"BduJhdHPpfhQLyponf48JzXSGZ8=",
           "nonce":"VOUFT-WwrEv0NuAQEHoV7Q",
           "assertion":"proximity",
           "truncated":"0"
       },
       {
           "date":"2017-05-15T17:25:55.644-04:00",
           "domainID":"BduJhdHPpfhQLyponf48JzXSGZ8=",
           "nonce":"f4G6Vi1t8nKo/FieCVgpBg==",
           "assertion":"proximity"
       }
     ],
       "truncation": {
           "nonced duplicates": "0",
           "nonceless duplicates": "1",
           "arbitrary": "2"
        }
   }

                Figure 18: Example of an Audit-Log Response

   The domainID is a binary SubjectKeyIdentifier value calculated
   according to Section 5.8.2.  It is encoded once in base64 in order to
   be transported in this JSON container.

   The date is formatted per [RFC3339], which is consistent with typical
   JavaScript usage of JSON.

   The truncation structure MAY be omitted if all values are zero.  Any
   counter missing from the truncation structure is assumed to be zero.

   The nonce is a string, as provided in the voucher-request, and is
   used in the voucher.  If no nonce was placed in the resulting
   voucher, then a value of null SHOULD be used in preference to
   omitting the entry.  While the nonce is often created as a
   base64-encoded random series of bytes, this should not be assumed.

   Distribution of a large log is less than ideal.  This structure can
   be optimized as follows: nonced or nonceless entries for the same
   domainID MAY be abridged from the log leaving only the single most
   recent nonced or nonceless entry for that domainID.  In the case of
   truncation, the "event" truncation value SHOULD contain a count of
   the number of events for this domainID that were omitted.  The log
   SHOULD NOT be further reduced, but an operational situation could
   exist where maintaining the full log is not possible.  In such
   situations, the log MAY be arbitrarily abridged for length, with the
   number of removed entries indicated as "arbitrary".

   If the truncation count exceeds 1024, then the MASA MAY use this
   value without further incrementing it.

   A log where duplicate entries for the same domain have been omitted
   ("nonced duplicates" and/or "nonceless duplicates") could still be
   acceptable for informed decisions.  A log that has had "arbitrary"
   truncations is less acceptable, but manufacturer transparency is
   better than hidden truncations.

   A registrar that sees a version value greater than 1 indicates an
   audit-log format that has been enhanced with additional information.
   No information will be removed in future versions; should an
   incompatible change be desired in the future, then a new HTTP
   endpoint will be used.

   This document specifies a simple log format as provided by the MASA
   service to the registrar.  This format could be improved by
   distributed consensus technologies that integrate vouchers with
   technologies such as block-chain or hash trees or optimized logging
   approaches.  Doing so is out of the scope of this document but is an
   anticipated improvement for future work.  As such, the registrar
   SHOULD anticipate new kinds of responses and SHOULD provide operator
   controls to indicate how to process unknown responses.

5.8.2.  Calculation of domainID

   The domainID is a binary value (a BIT STRING) that uniquely
   identifies a registrar by the pinned-domain-cert.

   If the pinned-domain-cert certificate includes the
   SubjectKeyIdentifier ([RFC5280], Section 4.2.1.2), then it is used as
   the domainID.  If not, the SPKI Fingerprint as described in
   [RFC7469], Section 2.4 is used.  This value needs to be calculated by
   both the MASA (to populate the audit-log) and the registrar (to
   recognize itself in the audit-log).

   [RFC5280], Section 4.2.1.2 does not mandate that the
   SubjectKeyIdentifier extension be present in non-CA certificates.  It
   is RECOMMENDED that registrar certificates (even if self-signed)
   always include the SubjectKeyIdentifier to be used as a domainID.

   The domainID is determined from the certificate chain associated with
   the pinned-domain-cert and is used to update the audit-log.

5.8.3.  Registrar Audit-Log Verification

   Each time the MASA issues a voucher, it appends details of the
   assignment to an internal audit-log for that device.  The internal
   audit-log is processed when responding to requests for details as
   described in Section 5.8.  The contents of the audit-log can express
   a variety of trust levels, and this section explains what kind of
   trust a registrar can derive from the entries.

   While the audit-log provides a list of vouchers that were issued by
   the MASA, the vouchers are issued in response to voucher-requests,
   and it is the content of the voucher-requests that determines how
   meaningful the audit-log entries are.

   A registrar SHOULD use the log information to make an informed
   decision regarding the continued bootstrapping of the pledge.  The
   exact policy is out of scope of this document as it depends on the
   security requirements within the registrar domain.  Equipment that is
   purchased preowned can be expected to have an extensive history.  The
   following discussion is provided to help explain the value of each
   log element:

   date:  The date field provides the registrar an opportunity to divide
      the log around known events such as the purchase date.  Depending
      on the context known to the registrar or administrator, events
      before/after certain dates can have different levels of
      importance.  For example, for equipment that is expected to be
      new, and thus has no history, it would be a surprise to find prior
      entries.

   domainID:  If the log includes an unexpected domainID, then the
      pledge could have imprinted on an unexpected domain.  The
      registrar can be expected to use a variety of techniques to define
      "unexpected" ranging from acceptlists of prior domains to anomaly
      detection (e.g., "this device was previously bound to a different
      domain than any other device deployed").  Log entries can also be
      compared against local history logs in search of discrepancies
      (e.g., "this device was re-deployed some number of times
      internally, but the external audit-log shows additional re-
      deployments our internal logs are unaware of").

   nonce:  Nonceless entries mean the logged domainID could
      theoretically trigger a reset of the pledge and then take over
      management by using the existing nonceless voucher.

   assertion:  The assertion leaf in the voucher and audit-log indicates
      why the MASA issued the voucher.  A "verified" entry means that
      the MASA issued the associated voucher as a result of positive
      verification of ownership.  However, this entry does not indicate
      whether or not the pledge was actually deployed in the prior
      domain.  A "logged" assertion informs the registrar that the prior
      vouchers were issued with minimal verification.  A "proximity"
      assertion assures the registrar that the pledge was truly
      communicating with the prior domain and thus provides assurance
      that the prior domain really has deployed the pledge.

   A relatively simple policy is to acceptlist known (internal or
   external) domainIDs and require all vouchers to have a nonce.  An
   alternative is to require that all nonceless vouchers be from a
   subset (e.g., only internal) of domainIDs.  If the policy is
   violated, a simple action is to revoke any locally issued credentials
   for the pledge in question or to refuse to forward the voucher.  The
   registrar MUST then refuse any EST actions and SHOULD inform a human
   via a log.  A registrar MAY be configured to ignore (i.e., override
   the above policy) the history of the device, but it is RECOMMENDED
   that this only be configured if hardware-assisted (i.e., Transport
   Performance Metrics (TPM) anchored) Network Endpoint Assessment (NEA)
   [RFC5209] is supported.

5.9.  EST Integration for PKI Bootstrapping

   The pledge SHOULD follow the BRSKI operations with EST enrollment
   operations including "CA Certificates Request", "CSR Attributes
   Request", and "Client Certificate Request" or "Server-Side Key
   Generation", etc.  This is a relatively seamless integration since
   BRSKI API calls provide an automated alternative to the manual
   bootstrapping method described in [RFC7030].  As noted above, use of
   HTTP-persistent connections simplifies the pledge state machine.

   Although EST allows clients to obtain multiple certificates by
   sending multiple Certificate Signing Requests (CSRs), BRSKI does not
   support this mechanism directly.  This is because BRSKI pledges MUST
   use the CSR Attributes request ([RFC7030], Section 4.5).  The
   registrar MUST validate the CSR against the expected attributes.
   This implies that client requests will "look the same" and therefore
   result in a single logical certificate being issued even if the
   client were to make multiple requests.  Registrars MAY contain more
   complex logic, but doing so is out of scope of this specification.
   BRSKI does not signal any enhancement or restriction to this
   capability.

5.9.1.  EST Distribution of CA Certificates

   The pledge SHOULD request the full EST Distribution of CA certificate
   messages; see [RFC7030], Section 4.1.

   This ensures that the pledge has the complete set of current CA
   certificates beyond the pinned-domain-cert (see Section 5.6.2 for a
   discussion of the limitations inherent in having a single certificate
   instead of a full CA certificate response).  Although these
   limitations are acceptable during initial bootstrapping, they are not
   appropriate for ongoing PKIX end-entity certificate validation.

5.9.2.  EST CSR Attributes

   Automated bootstrapping occurs without local administrative
   configuration of the pledge.  In some deployments, it is plausible
   that the pledge generates a certificate request containing only
   identity information known to the pledge (essentially the X.509
   IDevID information) and ultimately receives a certificate containing
   domain-specific identity information.  Conceptually, the CA has
   complete control over all fields issued in the end-entity
   certificate.  Realistically, this is operationally difficult with the
   current status of PKI CA deployments, where the CSR is submitted to
   the CA via a number of non-standard protocols.  Even with all
   standardized protocols used, it could operationally be problematic to
   expect that service-specific certificate fields can be created by a
   CA that is likely operated by a group that has no insight into
   different network services/protocols used.  For example, the CA could
   even be outsourced.

   To alleviate these operational difficulties, the pledge MUST request
   the EST "CSR Attributes" from the EST server, and the EST server
   needs to be able to reply with the attributes necessary for use of
   the certificate in its intended protocols/services.  This approach
   allows for minimal CA integrations, and instead, the local
   infrastructure (EST server) informs the pledge of the proper fields
   to include in the generated CSR (such as rfc822Name).  This approach
   is beneficial to automated bootstrapping in the widest number of
   environments.

   In networks using the BRSKI enrolled certificate to authenticate the
   ACP, the EST CSR Attributes MUST include the ACP domain information
   fields defined in [RFC8994], Section 6.2.2.

   The registrar MUST also confirm that the resulting CSR is formatted
   as indicated before forwarding the request to a CA.  If the registrar
   is communicating with the CA using a protocol such as full
   Certificate Management over CMS (CMC), which provides mechanisms to
   override the CSR Attributes, then these mechanisms MAY be used even
   if the client ignores the guidance for the CSR Attributes.

5.9.3.  EST Client Certificate Request

   The pledge MUST request a new Client Certificate; see [RFC7030],
   Section 4.2.

5.9.4.  Enrollment Status Telemetry

   For automated bootstrapping of devices, the administrative elements
   that provide bootstrapping also provide indications to the system
   administrators concerning device life-cycle status.  This might
   include information concerning attempted bootstrapping messages seen
   by the client.  The MASA provides logs and the status of credential
   enrollment.  Since an end user is assumed per [RFC7030], a final
   success indication back to the server is not included.  This is
   insufficient for automated use cases.

   The client MUST send an indicator to the registrar about its
   enrollment status.  It does this by using an HTTP POST of a JSON
   dictionary with the attributes described below to the new EST
   endpoint at "/.well-known/brski/enrollstatus".

   When indicating a successful enrollment, the client SHOULD first re-
   establish the EST TLS session using the newly obtained credentials.
   TLS 1.3 supports doing this in-band, but TLS 1.2 does not.  The
   client SHOULD therefore always close the existing TLS connection and
   start a new one, using the same Join Proxy.

   In the case of a failed enrollment, the client MUST send the
   telemetry information over the same TLS connection that was used for
   the enrollment attempt, with a Reason string indicating why the most
   recent enrollment failed.  (For failed attempts, the TLS connection
   is the most reliable way to correlate server-side information with
   what the client provides.)

   The version and status fields MUST be present.  The Reason field
   SHOULD be present whenever the status field is false.  In the case of
   a SUCCESS, the Reason string MAY be omitted.

   The reason-context attribute is an arbitrary JSON object (literal
   value or hash of values) that provides additional information
   specific to the failure to unroll from this pledge.  The contents of
   this field are not subject to standardization.  This is represented
   by the group-socket "$$arbitrary-map" in the CDDL.

   <CODE BEGINS> file "enrollstatus.cddl"
   enrollstatus-post = {
       "version": uint,
       "status": bool,
       ? "reason": text,
       ? "reason-context" : { $$arbitrary-map }
     }
   }
   <CODE ENDS>

                 Figure 19: CDDL for Enrollment Status POST

   An example status report can be seen below.  It is sent with the
   media type: application/json

   {
       "version": 1,
       "status":true,
       "reason":"Informative human readable message",
       "reason-context": { "additional" : "JSON" }
   }

                Figure 20: Example of Enrollment Status POST

   The server SHOULD respond with an HTTP 200 but MAY simply fail with
   an HTTP 404 error.

   Within the server logs, the server MUST capture if this message was
   received over a TLS session with a matching Client Certificate.

5.9.5.  Multiple Certificates

   Pledges that require multiple certificates could establish direct EST
   connections to the registrar.

5.9.6.  EST over CoAP

   This document describes extensions to EST for the purpose of
   bootstrapping remote key infrastructures.  Bootstrapping is relevant
   for CoAP enrollment discussions as well.  The definition of EST and
   BRSKI over CoAP is not discussed within this document beyond ensuring
   proxy support for CoAP operations.  Instead, it is anticipated that a
   definition of CoAP mappings will occur in subsequent documents such
   as [ACE-COAP-EST] and that CoAP mappings for BRSKI will be discussed
   either there or in future work.

6.  Clarification of Transfer-Encoding

   [RFC7030] defines endpoints to include a "Content-Transfer-Encoding"
   heading and payloads to be base64-encoded DER [RFC4648].

   When used within BRSKI, the original EST endpoints remain base64
   encoded [RFC7030] (as clarified by [RFC8951]), but the new BRSKI
   endpoints that send and receive binary artifacts (specifically,
   "/.well-known/brski/requestvoucher") are binary.  That is, no
   encoding is used.

   In the BRSKI context, the EST "Content-Transfer-Encoding" header
   field SHOULD be ignored if present.  This header field does not need
   to be included.

7.  Reduced Security Operational Modes

   A common requirement of bootstrapping is to support less secure
   operational modes for support-specific use cases.  This section
   suggests a range of mechanisms that would alter the security
   assurance of BRSKI to accommodate alternative deployment
   architectures and mitigate life-cycle management issues identified in
   Section 10.  They are presented here as informative (non-normative)
   design guidance for future standardization activities.  Section 9
   provides standardization applicability statements for the ANIMA ACP.
   Other users would expect that subsets of these mechanisms could be
   profiled with accompanying applicability statements similar to the
   one described in Section 9.

   This section is considered non-normative in the generality of the
   protocol.  Use of the suggested mechanisms here MUST be detailed in
   specific profiles of BRSKI, such as in Section 9.

7.1.  Trust Model

   This section explains the trust relationships detailed in
   Section 2.4:

   +--------+         +---------+    +------------+     +------------+
   | Pledge |         | Join    |    | Domain     |     |Manufacturer|
   |        |         | Proxy   |    | Registrar  |     | Service    |
   |        |         |         |    |            |     | (Internet) |
   +--------+         +---------+    +------------+     +------------+

                  Figure 21: Elements of BRSKI Trust Model

   Pledge:  The pledge could be compromised and provide an attack vector
      for malware.  The entity is trusted to only imprint using secure
      methods described in this document.  Additional endpoint
      assessment techniques are RECOMMENDED but are out of scope of this
      document.

   Join Proxy:  Provides proxy functionalities but is not involved in
      security considerations.

   Registrar:  When interacting with a MASA, a registrar makes all
      decisions.  For Ownership Audit Vouchers (see [RFC8366]), the
      registrar is provided an opportunity to accept MASA decisions.

   Vendor Service, MASA:  This form of manufacturer service is trusted
      to accurately log all claim attempts and to provide authoritative
      log information to registrars.  The MASA does not know which
      devices are associated with which domains.  These claims could be
      strengthened by using cryptographic log techniques to provide
      append only, cryptographic assured, publicly auditable logs.

   Vendor Service, Ownership Validation:  This form of manufacturer
      service is trusted to accurately know which device is owned by
      which domain.

7.2.  Pledge Security Reductions

   The following is a list of alternative behaviors that the pledge can
   be programmed to implement.  These behaviors are not mutually
   exclusive, nor are they dependent upon each other.  Some of these
   methods enable offline and emergency (touch-based) deployment use
   cases.  Normative language is used as these behaviors are referenced
   in later sections in a normative fashion.

   1.  The pledge MUST accept nonceless vouchers.  This allows for a use
       case where the registrar cannot connect to the MASA at the
       deployment time.  Logging and validity periods address the
       security considerations of supporting these use cases.

   2.  Many devices already support "trust on first use" for physical
       interfaces such as console ports.  This document does not change
       that reality.  Devices supporting this protocol MUST NOT support
       "trust on first use" on network interfaces.  This is because
       "trust on first use" over network interfaces would undermine the
       logging based security protections provided by this
       specification.

   3.  The pledge MAY have an operational mode where it skips voucher
       validation one time, for example, if a physical button is
       depressed during the bootstrapping operation.  This can be useful
       if the manufacturer service is unavailable.  This behavior SHOULD
       be available via local configuration or physical presence methods
       (such as use of a serial/craft console) to ensure new entities
       can always be deployed even when autonomic methods fail.  This
       allows for unsecured imprint.

   4.  A craft/serial console could include a command such as "est-
       enroll [2001:db8:0:1]:443" that begins the EST process from the
       point after the voucher is validated.  This process SHOULD
       include server certificate verification using an on-screen
       fingerprint.

   It is RECOMMENDED that "trust on first use" or any method of skipping
   voucher validation (including use of a craft serial console) only be
   available if hardware-assisted Network Endpoint Assessment (NEA)
   [RFC5209] is supported.  This recommendation ensures that domain
   network monitoring can detect inappropriate use of offline or
   emergency deployment procedures when voucher-based bootstrapping is
   not used.

7.3.  Registrar Security Reductions

   A registrar can choose to accept devices using less secure methods.
   They MUST NOT be the default behavior.  These methods may be
   acceptable in situations where threat models indicate that low
   security is adequate.  This includes situations where security
   decisions are being made by the local administrator:

   1.  A registrar MAY choose to accept all devices, or all devices of a
       particular type.  The administrator could make this choice in
       cases where it is operationally difficult to configure the
       registrar with the unique identifier of each new device expected.

   2.  A registrar MAY choose to accept devices that claim a unique
       identity without the benefit of authenticating that claimed
       identity.  This could occur when the pledge does not include an
       X.509 IDevID factory-installed credential.  New entities without
       an X.509 IDevID credential MAY form the request per Section 5.2
       using the format per Section 5.5 to ensure the pledge's serial
       number information is provided to the registrar (this includes
       the IDevID AuthorityKeyIdentifier value, which would be
       statically configured on the pledge).  The pledge MAY refuse to
       provide a TLS Client Certificate (as one is not available).  The
       pledge SHOULD support HTTP-based or certificate-less TLS
       authentication as described in EST [RFC7030], Section 3.3.2.  A
       registrar MUST NOT accept unauthenticated new entities unless it
       has been configured to do so by an administrator that has
       verified that only expected new entities can communicate with a
       registrar (presumably via a physically secured perimeter.)

   3.  A registrar MAY submit a nonceless voucher-request to the MASA
       service (by not including a nonce in the voucher-request).  The
       resulting vouchers can then be stored by the registrar until they
       are needed during bootstrapping operations.  This is for use
       cases where the target network is protected by an air gap and
       therefore cannot contact the MASA service during pledge
       deployment.

   4.  A registrar MAY ignore unrecognized nonceless log entries.  This
       could occur when used equipment is purchased with a valid history
       of being deployed in air gap networks that required offline
       vouchers.

   5.  A registrar MAY accept voucher formats of future types that
       cannot be parsed by the registrar.  This reduces the registrar's
       visibility into the exact voucher contents but does not change
       the protocol operations.

7.4.  MASA Security Reductions

   Lower security modes chosen by the MASA service affect all device
   deployments unless the lower security behavior is tied to specific
   device identities.  The modes described below can be applied to
   specific devices via knowledge of what devices were sold.  They can
   also be bound to specific customers (independent of the device
   identity) by authenticating the customer's registrar.

7.4.1.  Issuing Nonceless Vouchers

   A MASA has the option of not including a nonce in the voucher and/or
   not requiring one to be present in the voucher-request.  This results
   in distribution of a voucher that may never expire and, in effect,
   makes the specified domain an always trusted entity to the pledge
   during any subsequent bootstrapping attempts.  The log information
   captures when a nonceless voucher is issued so that the registrar can
   make appropriate security decisions when a pledge joins the domain.
   Nonceless vouchers are useful to support use cases where registrars
   might not be online during actual device deployment.

   While a nonceless voucher may include an expiry date, a typical use
   for a nonceless voucher is for it to be long lived.  If the device
   can be trusted to have an accurate clock (the MASA will know), then a
   nonceless voucher CAN be issued with a limited lifetime.

   A more typical case for a nonceless voucher is for use with offline
   onboarding scenarios where it is not possible to pass a fresh
   voucher-request to the MASA.  The use of a long-lived voucher also
   eliminates concern about the availability of the MASA many years in
   the future.  Thus, many nonceless vouchers will have no expiry dates.

   Thus, the long-lived nonceless voucher does not require proof that
   the device is online.  Issuing such a thing is only accepted when the
   registrar is authenticated by the MASA and the MASA is authorized to
   provide this functionality to this customer.  The MASA is RECOMMENDED
   to use this functionality only in concert with an enhanced level of
   ownership tracking, the details of which are out of scope for this
   document.

   If the pledge device is known to have a real-time clock that is set
   from the factory, use of a voucher validity period is RECOMMENDED.

7.4.2.  Trusting Owners on First Use

   A MASA has the option of not verifying ownership before responding
   with a voucher.  This is expected to be a common operational model
   because doing so relieves the manufacturer providing MASA services
   from having to track ownership during shipping and throughout the
   supply chain, and it allows for a very low overhead MASA service.  A
   registrar uses the audit-log information as an in-depth defense
   strategy to ensure that this does not occur unexpectedly (for
   example, when purchasing new equipment, the registrar would throw an
   error if any audit-log information is reported).  The MASA SHOULD
   verify the prior-signed-voucher-request information for pledges that
   support that functionality.  This provides a proof-of-proximity check
   that reduces the need for ownership verification.  The proof-of-
   proximity comes from the assumption that the pledge and Join Proxy
   are on the same link-local connection.

   A MASA that practices TOFU for registrar identity may wish to
   annotate the origin of the connection by IP address or netblock and
   restrict future use of that identity from other locations.  A MASA
   that does this SHOULD take care to not create nuisance situations for
   itself when a customer has multiple registrars or uses outgoing IPv4-
   to-IPv4 NAT (NAT44) connections that change frequently.

7.4.3.  Updating or Extending Voucher Trust Anchors

   This section deals with two problems: A MASA that is no longer
   available due to a failed business and a MASA that is uncooperative
   to a secondary sale.

   A manufacturer could offer a management mechanism that allows the
   list of voucher verification trust anchors to be extended.
   [YANG-KEYSTORE] describes one such interface that could be
   implemented using YANG.  Pretty much any configuration mechanism used
   today could be extended to provide the needed additional update.  A
   manufacturer could even decide to install the domain CA trust anchors
   received during the EST "cacerts" step as voucher verification
   anchors.  Some additional signals will be needed to clearly identify
   which keys have voucher validation authority from among those signed
   by the domain CA.  This is future work.

   With the above change to the list of anchors, vouchers can be issued
   by an alternate MASA.  This could be the previous owner (the seller)
   or some other trusted third party who is mediating the sale.  If it
   is a third party, the seller would need to take steps to introduce
   the third-party configuration to the device prior to disconnection.
   The third party (e.g., a wholesaler of used equipment) could,
   however, use a mechanism described in Section 7.2 to take control of
   the device after receiving it physically.  This would permit the
   third party to act as the MASA for future onboarding actions.  As the
   IDevID certificate probably cannot be replaced, the new owner's
   registrar would have to support an override of the MASA URL.

   To be useful for resale or other transfers of ownership, one of two
   situations will need to occur.  The simplest is that the device is
   not put through any kind of factory default/reset before going
   through onboarding again.  Some other secure, physical signal would
   be needed to initiate it.  This is most suitable for redeploying a
   device within the same enterprise.  This would entail having previous
   configuration in the system until entirely replaced by the new owner,
   and it represents some level of risk.

   For the second scenario, there would need to be two levels of factory
   reset.  One would take the system back entirely to manufacturer
   state, including removing any added trust anchors, and the other
   (more commonly used) one would just restore the configuration back to
   a known default without erasing trust anchors.  This weaker factory
   reset might leave valuable credentials on the device, and this may be
   unacceptable to some owners.

   As a third option, the manufacturer's trust anchors could be entirely
   overwritten with local trust anchors.  A factory default would never
   restore those anchors.  This option comes with a lot of power but is
   also a lot of responsibility: if access to the private part of the
   new anchors are lost, the manufacturer may be unable to help.

8.  IANA Considerations

   Per this document, IANA has completed the following actions.

8.1.  The IETF XML Registry

   This document registers a URI in the "IETF XML Registry" [RFC3688].
   IANA has registered the following:

   URI:  urn:ietf:params:xml:ns:yang:ietf-voucher-request
   Registrant Contact:  The ANIMA WG of the IETF.
   XML:  N/A; the requested URI is an XML namespace.

8.2.  YANG Module Names Registry

   This document registers a YANG module in the "YANG Module Names"
   registry [RFC6020].  IANA has registered the following:

   Name:  ietf-voucher-request
   Namespace:  urn:ietf:params:xml:ns:yang:ietf-voucher-request
   Prefix:  vch
   Reference:  RFC 8995

8.3.  BRSKI Well-Known Considerations

8.3.1.  BRSKI .well-known Registration

   To the "Well-Known URIs" registry at
   https://www.iana.org/assignments/well-known-uris/, this document
   registers the well-known name "brski" with the following filled-in
   template from [RFC8615]:

   URI Suffix:  brski
   Change Controller:  IETF

   IANA has changed the registration of "est" to now only include
   [RFC7030] and no longer this document.  Earlier draft versions of
   this document used "/.well-known/est" rather than "/.well-known/
   brski".

8.3.2.  BRSKI .well-known Registry

   IANA has created a new registry entitled: "BRSKI Well-Known URIs".
   The registry has three columns: URI, Description, and Reference.  New
   items can be added using the Specification Required [RFC8126]
   process.  The initial contents of this registry are:

        +=================+==========================+===========+
        | URI             | Description              | Reference |
        +=================+==========================+===========+
        | requestvoucher  | pledge to registrar, and | RFC 8995  |
        |                 | from registrar to MASA   |           |
        +-----------------+--------------------------+-----------+
        | voucher_status  | pledge to registrar      | RFC 8995  |
        +-----------------+--------------------------+-----------+
        | requestauditlog | registrar to MASA        | RFC 8995  |
        +-----------------+--------------------------+-----------+
        | enrollstatus    | pledge to registrar      | RFC 8995  |
        +-----------------+--------------------------+-----------+

                      Table 1: BRSKI Well-Known URIs

8.4.  PKIX Registry

   IANA has registered the following:

   a number for id-mod-MASAURLExtn2016(96) from the pkix(7) id-mod(0)
   Registry.

   IANA has assigned a number from the id-pe registry (Structure of
   Management Information (SMI) Security for PKIX Certificate Extension)
   for id-pe-masa-url with the value 32, resulting in an OID of
   1.3.6.1.5.5.7.1.32.

8.5.  Pledge BRSKI Status Telemetry

   IANA has created a new registry entitled "BRSKI Parameters" and has
   created, within that registry, a table called: "Pledge BRSKI Status
   Telemetry Attributes".  New items can be added using the
   Specification Required process.  The following items are in the
   initial registration, with this document (see Section 5.7) as the
   reference:

   *  version

   *  Status

   *  Reason

   *  reason-context

8.6.  DNS Service Names

   IANA has registered the following service names:

   Service Name:  brski-proxy
   Transport Protocol(s):  tcp
   Assignee:  IESG <iesg@ietf.org>
   Contact:  IESG <iesg@ietf.org>
   Description:  The Bootstrapping Remote Secure Key Infrastructure
      Proxy
   Reference:  RFC 8995

   Service Name:  brski-registrar
   Transport Protocol(s):  tcp
   Assignee:  IESG <iesg@ietf.org>
   Contact:  IESG <iesg@ietf.org>
   Description:  The Bootstrapping Remote Secure Key Infrastructure
      Registrar
   Reference:  RFC 8995

8.7.  GRASP Objective Names

   IANA has registered the following GRASP Objective Names:

   IANA has registered the value "AN_Proxy" (without quotes) to the
   "GRASP Objective Names" table in the GRASP Parameter registry.  The
   specification for this value is Section 4.1.1 of this document.

   The IANA has registered the value "AN_join_registrar" (without
   quotes) to the "GRASP Objective Names" table in the GRASP Parameter
   registry.  The specification for this value is Section 4.3 of this
   document.

9.  Applicability to the Autonomic Control Plane (ACP)

   This document provides a solution to the requirements for secure
   bootstrapping as defined in "Using an Autonomic Control Plane for
   Stable Connectivity of Network Operations, Administration, and
   Maintenance (OAM)" [RFC8368], "A Reference Model for Autonomic
   Networking" [RFC8993], and specifically "An Autonomic Control Plane
   (ACP)" [RFC8994]; see Sections 3.2 ("Secure Bootstrap over an
   Unconfigured Network") and 6.2 ("ACP Domain, Certificate, and
   Network").

   The protocol described in this document has appeal in a number of
   other non-ANIMA use cases.  Such uses of the protocol will be
   deployed into other environments with different tradeoffs of privacy,
   security, reliability, and autonomy from manufacturers.  As such,
   those use cases will need to provide their own applicability
   statements and will need to address unique privacy and security
   considerations for the environments in which they are used.

   The ACP that is bootstrapped by the BRSKI protocol is typically used
   in medium to large Internet service provider organizations.
   Equivalent enterprises that have significant Layer 3 router
   connectivity also will find significant benefit, particularly if the
   enterprise has many sites.  (A network consisting of primarily Layer
   2 is not excluded, but the adjacencies that the ACP will create and
   maintain will not reflect the topology until all devices participate
   in the ACP.)

   In the ACP, the Join Proxy is found to be proximal because
   communication between the pledge and the Join Proxy is exclusively on
   IPv6 link-local addresses.  The proximity of the Join Proxy to the
   registrar is validated by the registrar using ANI ACP IPv6 ULAs.
   ULAs are not routable over the Internet, so as long as the Join Proxy
   is operating correctly, the proximity assertion is satisfied.  Other
   uses of BRSKI will need similar analysis if they use proximity
   assertions.

   As specified in the ANIMA charter, this work "focuses on
   professionally-managed networks."  Such a network has an operator and
   can do things like install, configure, and operate the registrar
   function.  The operator makes purchasing decisions and is aware of
   what manufacturers it expects to see on its network.

   Such an operator is also capable of performing bootstrapping of a
   device using a serial console (craft console).  The zero-touch
   mechanism presented in this and the ACP document [RFC8994] represents
   a significant efficiency: in particular, it reduces the need to put
   senior experts on airplanes to configure devices in person.

   As the technology evolves, there is recognition that not every
   situation may work out, and occasionally a human may still have to
   visit.  Given this, some mechanisms are presented in Section 7.2.
   The manufacturer MUST provide at least one of the one-touch
   mechanisms described that permit enrollment to proceed without the
   availability of any manufacturer server (such as the MASA).

   The BRSKI protocol is going into environments where there have
   already been quite a number of vendor proprietary management systems.
   Those are not expected to go away quickly but rather to leverage the
   secure credentials that are provisioned by BRSKI.  The connectivity
   requirements of the said management systems are provided by the ACP.

9.1.  Operational Requirements

   This section collects operational requirements based upon the three
   roles involved in BRSKI: the MASA, the (domain) owner, and the
   device.  It should be recognized that the manufacturer may be
   involved in two roles, as it creates the software/firmware for the
   device and may also be the operator of the MASA.

   The requirements in this section are presented using BCP 14 language
   [RFC2119] [RFC8174].  These do not represent new normative
   statements, just a review of a few such things in one place by role.
   They also apply specifically to the ANIMA ACP use case.  Other use
   cases likely have similar, but MAY have different, requirements.

9.1.1.  MASA Operational Requirements

   The manufacturer MUST arrange for an online service called the MASA
   to be available.  It MUST be available at the URL that is encoded in
   the IDevID certificate extensions described in Section 2.3.2.

   The online service MUST have access to a private key with which to
   sign voucher artifacts [RFC8366].  The public key, certificate, or
   certificate chain MUST be built into the device as part of the
   firmware.

   It is RECOMMENDED that the manufacturer arrange for this signing key
   (or keys) to be escrowed according to typical software source code
   escrow practices [softwareescrow].

   The MASA accepts voucher-requests from domain owners according to an
   operational practice appropriate for the device.  This can range from
   any domain owner (first-come first-served, on a TOFU-like basis), to
   full sales channel integration where domain owners need to be
   positively identified by TLS pinned Client Certificates or an HTTP
   authentication process.  The MASA creates signed voucher artifacts
   according to its internally defined policies.

   The MASA MUST operate an audit-log for devices that is accessible.
   The audit-log is designed to be easily cacheable, and the MASA MAY
   find it useful to put this content on a Content Delivery Network
   (CDN).

9.1.2.  Domain Owner Operational Requirements

   The domain owner MUST operate an EST [RFC7030] server with the
   extensions described in this document.  This is the JRC or registrar.
   This JRC/EST server MUST announce itself using GRASP within the ACP.
   This EST server will typically reside with the Network Operations
   Center for the organization.

   The domain owner MAY operate an internal CA that is separate from the
   EST server, or it MAY combine all activities into a single device.
   The determination of the architecture depends upon the scale and
   resiliency requirements of the organization.  Multiple JRC instances
   MAY be announced into the ACP from multiple locations to achieve an
   appropriate level of redundancy.

   In order to recognize which devices and which manufacturers are
   welcome on the domain owner's network, the domain owner SHOULD
   maintain an acceptlist of manufacturers.  This MAY extend to
   integration with purchasing departments to know the serial numbers of
   devices.

   The domain owner SHOULD use the resulting overlay ACP network to
   manage devices, replacing legacy out-of-band mechanisms.

   The domain owner SHOULD operate one or more EST servers that can be
   used to renew the domain certificates (LDevIDs), which are deployed
   to devices.  These servers MAY be the same as the JRC or MAY be a
   distinct set of devices, as appropriate for resiliency.

   The organization MUST take appropriate precautions against loss of
   access to the CA private key.  Hardware security modules and/or
   secret splitting are appropriate.

9.1.3.  Device Operational Requirements

   Devices MUST come with built-in trust anchors that permit the device
   to validate vouchers from the MASA.

   Devices MUST come with (unique, per-device) IDevID certificates that
   include their serial numbers and the MASA URL extension.

   Devices are expected to find Join Proxies using GRASP, and then
   connect to the JRC using the protocol described in this document.

   Once a domain owner has been validated with the voucher, devices are
   expected to enroll into the domain using EST.  Devices are then
   expected to form ACPs using IPsec over IPv6 link-local addresses as
   described in [RFC8994].

   Once a device has been enrolled, it SHOULD listen for the address of
   the JRC using GRASP, and it SHOULD enable itself as a Join Proxy and
   announce itself on all links/interfaces using GRASP DULL.

   Devices are expected to renew their certificates before they expire.

10.  Privacy Considerations

10.1.  MASA Audit-Log

   The MASA audit-log includes the domainID for each domain a voucher
   has been issued to.  This information is closely related to the
   actual domain identity.  A MASA may need additional defenses against
   Denial-of-Service attacks (Section 11.1), and this may involve
   collecting additional (unspecified here) information.  This could
   provide sufficient information for the MASA service to build a
   detailed understanding of the devices that have been provisioned
   within a domain.

   There are a number of design choices that mitigate this risk.  The
   domain can maintain some privacy since it has not necessarily been
   authenticated and is not authoritatively bound to the supply chain.

   Additionally, the domainID captures only the unauthenticated subject
   key identifier of the domain.  A privacy-sensitive domain could
   theoretically generate a new domainID for each device being deployed.
   Similarly, a privacy-sensitive domain would likely purchase devices
   that support proximity assertions from a manufacturer that does not
   require sales channel integrations.  This would result in a
   significant level of privacy while maintaining the security
   characteristics provided by the registrar-based audit-log inspection.

10.2.  What BRSKI-EST Reveals

   During the provisional phase of the BRSKI-EST connection between the
   pledge and the registrar, each party reveals its certificates to each
   other.  For the pledge, this includes the serialNumber attribute, the
   MASA URL, and the identity that signed the IDevID certificate.

   TLS 1.2 reveals the certificate identities to on-path observers,
   including the Join Proxy.

   TLS 1.3 reveals the certificate identities only to the end parties,
   but as the connection is provisional; an on-path attacker (MITM) can
   see the certificates.  This includes not just malicious attackers but
   also registrars that are visible to the pledge but are not part of
   the intended domain.

   The certificate of the registrar is rather arbitrary from the point
   of view of the BRSKI protocol.  As no validations [RFC6125] are
   expected to be done, the contents could be easily pseudonymized.  Any
   device that can see a Join Proxy would be able to connect to the
   registrar and learn the identity of the network in question.  Even if
   the contents of the certificate are pseudonymized, it would be
   possible to correlate different connections in different locations
   that belong to the same entity.  This is unlikely to present a
   significant privacy concern to ANIMA ACP uses of BRSKI, but it may be
   a concern to other users of BRSKI.

   The certificate of the pledge could be revealed by a malicious Join
   Proxy that performed a MITM attack on the provisional TLS connection.
   Such an attacker would be able to reveal the identity of the pledge
   to third parties if it chose to do so.

   Research into a mechanism to do multistep, multiparty authenticated
   key agreement, incorporating some kind of zero-knowledge proof, would
   be valuable.  Such a mechanism would ideally avoid disclosing
   identities until the pledge, registrar, and MASA agree to the
   transaction.  Such a mechanism would need to discover the location of
   the MASA without knowing the identity of the pledge or the identity
   of the MASA.  This part of the problem may be unsolvable.

10.3.  What BRSKI-MASA Reveals to the Manufacturer

   With consumer-oriented devices, the "call-home" mechanism in IoT
   devices raises significant privacy concerns.  See [livingwithIoT] and
   [IoTstrangeThings] for exemplars.  The ACP usage of BRSKI is not
   targeted at individual usage of IoT devices but rather at the
   enterprise and ISP creation of networks in a zero-touch fashion where
   the "call-home" represents a different class of privacy and life-
   cycle management concerns.

   It needs to be reiterated that the BRSKI-MASA mechanism only occurs
   once during the commissioning of the device.  It is well defined, and
   although encrypted with TLS, it could in theory be made auditable as
   the contents are well defined.  This connection does not occur when
   the device powers on or is restarted for normal routines.  (It is
   conceivable, but remarkably unusual, that a device could be forced to
   go through a full factory reset during an exceptional firmware update
   situation, after which enrollment would have to be repeated, and a
   new connection would occur.)

   The BRSKI call-home mechanism is mediated via the owner's registrar,
   and the information that is transmitted is directly auditable by the
   device owner.  This is in stark contrast to many "call-home"
   protocols where the device autonomously calls home and uses an
   undocumented protocol.

   While the contents of the signed part of the pledge voucher-request
   cannot be changed, they are not encrypted at the registrar.  The
   ability to audit the messages by the owner of the network is a
   mechanism to defend against exfiltration of data by a nefarious
   pledge.  Both are, to reiterate, encrypted by TLS while in transit.

   The BRSKI-MASA exchange reveals the following information to the
   manufacturer:

   *  the identity of the device being enrolled.  This is revealed by
      transmission of a signed voucher-request containing the serial-
      number.  The manufacturer can usually link the serial number to a
      device model.

   *  an identity of the domain owner in the form of the domain trust
      anchor.  However, this is not a global PKI-anchored name within
      the WebPKI, so this identity could be pseudonymous.  If there is
      sales channel integration, then the MASA will have authenticated
      the domain owner, via either a pinned certificate or perhaps
      another HTTP authentication method, as per Section 5.5.4.

   *  the time the device is activated.

   *  the IP address of the domain owner's registrar.  For ISPs and
      enterprises, the IP address provides very clear geolocation of the
      owner.  No amount of IP address privacy extensions [RFC8981] can
      do anything about this, as a simple whois lookup likely identifies
      the ISP or enterprise from the upper bits anyway.  A passive
      attacker who observes the connection definitely may conclude that
      the given enterprise/ISP is a customer of the particular equipment
      vendor.  The precise model that is being enrolled will remain
      private.

   Based upon the above information, the manufacturer is able to track a
   specific device from pseudonymous domain identity to the next
   pseudonymous domain identity.  If there is sales-channel integration,
   then the identities are not pseudonymous.

   The manufacturer knows the IP address of the registrar, but it cannot
   see the IP address of the device itself.  The manufacturer cannot
   track the device to a detailed physical or network location, only to
   the location of the registrar.  That is likely to be at the
   enterprise or ISP's headquarters.

   The above situation is to be distinguished from a residential/
   individual person who registers a device from a manufacturer.
   Individuals do not tend to have multiple offices, and their registrar
   is likely on the same network as the device.  A manufacturer that
   sells switching/routing products to enterprises should hardly be
   surprised if additional purchases of switching/routing products are
   made.  Deviations from a historical trend or an established baseline
   would, however, be notable.

   The situation is not improved by the enterprise/ISP using
   anonymization services such as Tor [Dingledine], as a TLS 1.2
   connection will reveal the ClientCertificate used, clearly
   identifying the enterprise/ISP involved.  TLS 1.3 is better in this
   regard, but an active attacker can still discover the parties
   involved by performing a MITM attack on the first attempt (breaking/
   killing it with a TCP reset (RST)), and then letting subsequent
   connection pass through.

   A manufacturer could attempt to mix the BRSKI-MASA traffic in with
   general traffic on their site by hosting the MASA behind the same
   (set) of load balancers that the company's normal marketing site is
   hosted behind.  This makes a lot of sense from a straight capacity
   planning point of view as the same set of services (and the same set
   of Distributed Denial-of-Service mitigations) may be used.
   Unfortunately, as the BRSKI-MASA connections include TLS
   ClientCertificate exchanges, this may easily be observed in TLS 1.2,
   and a traffic analysis may reveal it even in TLS 1.3.  This does not
   make such a plan irrelevant.  There may be other organizational
   reasons to keep the marketing site (which is often subject to
   frequent redesigns, outsourcing, etc.) separate from the MASA, which
   may need to operate reliably for decades.

10.4.  Manufacturers and Used or Stolen Equipment

   As explained above, the manufacturer receives information each time a
   device that is in factory-default mode does a zero-touch bootstrap
   and attempts to enroll into a domain owner's registrar.

   The manufacturer is therefore in a position to decline to issue a
   voucher if it detects that the new owner is not the same as the
   previous owner.

   1.  This can be seen as a feature if the equipment is believed to
       have been stolen.  If the legitimate owner notifies the
       manufacturer of the theft, then when the new owner brings the
       device up, if they use the zero-touch mechanism, the new
       (illegitimate) owner reveals their location and identity.

   2.  In the case of used equipment, the initial owner could inform the
       manufacturer of the sale, or the manufacturer may just permit
       resales unless told otherwise.  In which case, the transfer of
       ownership simply occurs.

   3.  A manufacturer could, however, decide not to issue a new voucher
       in response to a transfer of ownership.  This is essentially the
       same as the stolen case, with the manufacturer having decided
       that the sale was not legitimate.

   4.  There is a fourth case, if the manufacturer is providing
       protection against stolen devices.  The manufacturer then has a
       responsibility to protect the legitimate owner against fraudulent
       claims that the equipment was stolen.  In the absence of such
       manufacturer protection, such a claim would cause the
       manufacturer to refuse to issue a new voucher.  Should the device
       go through a deep factory reset (for instance, replacement of a
       damaged main board component), the device would not bootstrap.

   5.  Finally, there is a fifth case: the manufacturer has decided to
       end-of-line the device, or the owner has not paid a yearly
       support amount, and the manufacturer refuses to issue new
       vouchers at that point.  This last case is not new to the
       industry: many license systems are already deployed that have a
       significantly worse effect.

   This section has outlined five situations in which a manufacturer
   could use the voucher system to enforce what are clearly license
   terms.  A manufacturer that attempted to enforce license terms via
   vouchers would find it rather ineffective as the terms would only be
   enforced when the device is enrolled, and this is not (to repeat) a
   daily or even monthly occurrence.

10.5.  Manufacturers and Grey Market Equipment

   Manufacturers of devices often sell different products into different
   regional markets.  Which product is available in which market can be
   driven by price differentials, support issues (some markets may
   require manuals and tech support to be done in the local language),
   and government export regulation (such as whether strong crypto is
   permitted to be exported or permitted to be used in a particular
   market).  When a domain owner obtains a device from a different
   market (they can be new) and transfers it to a different location,
   this is called a Grey Market.

   A manufacturer could decide not to issue a voucher to an enterprise/
   ISP based upon their location.  There are a number of ways that this
   could be determined: from the geolocation of the registrar, from
   sales channel knowledge about the customer, and from what products
   are available or unavailable in that market.  If the device has a
   GPS, the coordinates of the device could even be placed into an
   extension of the voucher.

   The above actions are not illegal, and not new.  Many manufacturers
   have shipped crypto-weak (exportable) versions of firmware as the
   default on equipment for decades.  The first task of an enterprise/
   ISP has always been to login to a manufacturer system, show one's
   "entitlement" (country information, proof that support payments have
   been made), and receive either a new updated firmware or a license
   key that will activate the correct firmware.

   BRSKI permits the above process to be automated (in an autonomic
   fashion) and therefore perhaps encourages this kind of
   differentiation by reducing the cost of doing it.

   An issue that manufacturers will need to deal with in the above
   automated process is when a device is shipped to one country with one
   set of rules (or laws or entitlements), but the domain registry is in
   another one.  Which rules apply is something that will have to be
   worked out: the manufacturer could believe they are dealing with Grey
   Market equipment when they are simply dealing with a global
   enterprise.

10.6.  Some Mitigations for Meddling by Manufacturers

   The most obvious mitigation is not to buy the product.  Pick
   manufacturers that are up front about their policies and who do not
   change them gratuitously.

   Section 7.4.3 describes some ways in which a manufacturer could
   provide a mechanism to manage the trust anchors and built-in
   certificates (IDevID) as an extension.  There are a variety of
   mechanisms, and some may take a substantial amount of work to get
   exactly correct.  These mechanisms do not change the flow of the
   protocol described here but rather allow the starting trust
   assumptions to be changed.  This is an area for future
   standardization work.

   Replacement of the voucher validation anchors (usually pointing to
   the original manufacturer's MASA) with those of the new owner permits
   the new owner to issue vouchers to subsequent owners.  This would be
   done by having the selling (old) owner run a MASA.

   The BRSKI protocol depends upon a trust anchor and an identity on the
   device.  Management of these entities facilitates a few new
   operational modes without making any changes to the BRSKI protocol.
   Those modes include: offline modes where the domain owner operates an
   internal MASA for all devices, resell modes where the first domain
   owner becomes the MASA for the next (resold-to) domain owner, and
   services where an aggregator acquires a large variety of devices and
   then acts as a pseudonymized MASA for a variety of devices from a
   variety of manufacturers.

   Although replacement of the IDevID is not required for all modes
   described above, a manufacturer could support such a thing.  Some may
   wish to consider replacement of the IDevID as an indication that the
   device's warranty is terminated.  For others, the privacy
   requirements of some deployments might consider this a standard
   operating practice.

   As discussed at the end of Section 5.8.1, new work could be done to
   use a distributed consensus technology for the audit-log.  This would
   permit the audit-log to continue to be useful, even when there is a
   chain of MASA due to changes of ownership.

10.7.  Death of a Manufacturer

   A common concern has been that a manufacturer could go out of
   business, leaving owners of devices unable to get new vouchers for
   existing products.  Said products might have been previously deployed
   but need to be reinitialized, used, or kept in a warehouse as long-
   term spares.

   The MASA was named the Manufacturer *Authorized* Signing Authority to
   emphasize that it need not be the manufacturer itself that performs
   this.  It is anticipated that specialist service providers will come
   to exist that deal with the creation of vouchers in much the same way
   that many companies have outsourced email, advertising, and
   janitorial services.

   Further, it is expected that as part of any service agreement, the
   manufacturer would arrange to escrow appropriate private keys such
   that a MASA service could be provided by a third party.  This has
   routinely been done for source code for decades.

11.  Security Considerations

   This document details a protocol for bootstrapping that balances
   operational concerns against security concerns.  As detailed in the
   introduction, and touched on again in Section 7, the protocol allows
   for reduced security modes.  These attempt to deliver additional
   control to the local administrator and owner in cases where less
   security provides operational benefits.  This section goes into more
   detail about a variety of specific considerations.

   To facilitate logging and administrative oversight, in addition to
   triggering registrar verification of MASA logs, the pledge reports on
   the voucher parsing status to the registrar.  In the case of a
   failure, this information is informative to a potentially malicious
   registrar.  This is mandated anyway because of the operational
   benefits of an informed administrator in cases where the failure is
   indicative of a problem.  The registrar is RECOMMENDED to verify MASA
   logs if voucher status telemetry is not received.

   To facilitate truly limited clients, EST requires that the client
   MUST support a client authentication model (see [RFC7030],
   Section 3.3.2); Section 7 updates these requirements by stating that
   the registrar MAY choose to accept devices that fail cryptographic
   authentication.  This reflects current (poor) practices in shipping
   devices without a cryptographic identity that are NOT RECOMMENDED.

   During the provisional period of the connection, the pledge MUST
   treat all HTTP header and content data as untrusted data.  HTTP
   libraries are regularly exposed to non-secured HTTP traffic: mature
   libraries should not have any problems.

   Pledges might chose to engage in protocol operations with multiple
   discovered registrars in parallel.  As noted above, they will only do
   so with distinct nonce values, but the end result could be multiple
   vouchers issued from the MASA if all registrars attempt to claim the
   device.  This is not a failure, and the pledge chooses whichever
   voucher to accept based on internal logic.  The registrars verifying
   log information will see multiple entries and take this into account
   for their analytic purposes.

11.1.  Denial of Service (DoS) against MASA

   There are use cases where the MASA could be unavailable or
   uncooperative to the registrar.  They include active DoS attacks,
   planned and unplanned network partitions, changes to MASA policy, or
   other instances where MASA policy rejects a claim.  These introduce
   an operational risk to the registrar owner in that MASA behavior
   might limit the ability to bootstrap a pledge device.  For example,
   this might be an issue during disaster recovery.  This risk can be
   mitigated by registrars that request and maintain long-term copies of
   "nonceless" vouchers.  In that way, they are guaranteed to be able to
   bootstrap their devices.

   The issuance of nonceless vouchers themselves creates a security
   concern.  If the registrar of a previous domain can intercept
   protocol communications, then it can use a previously issued
   nonceless voucher to establish management control of a pledge device
   even after having sold it.  This risk is mitigated by recording the
   issuance of such vouchers in the MASA audit-log that is verified by
   the subsequent registrar and by pledges only bootstrapping when in a
   factory default state.  This reflects a balance between enabling MASA
   independence during future bootstrapping and the security of
   bootstrapping itself.  Registrar control over requesting and auditing
   nonceless vouchers allows device owners to choose an appropriate
   balance.

   The MASA is exposed to DoS attacks wherein attackers claim an
   unbounded number of devices.  Ensuring a registrar is representative
   of a valid manufacturer customer, even without validating ownership
   of specific pledge devices, helps to mitigate this.  Pledge
   signatures on the pledge voucher-request, as forwarded by the
   registrar in the prior-signed-voucher-request field of the registrar
   voucher-request, significantly reduce this risk by ensuring the MASA
   can confirm proximity between the pledge and the registrar making the
   request.  Supply-chain integration ("know your customer") is an
   additional step that MASA providers and device vendors can explore.

11.2.  DomainID Must Be Resistant to Second-Preimage Attacks

   The domainID is used as the reference in the audit-log to the domain.
   The domainID is expected to be calculated by a hash that is resistant
   to a second-preimage attack.  Such an attack would allow a second
   registrar to create audit-log entries that are fake.

11.3.  Availability of Good Random Numbers

   The nonce used by the pledge in the voucher-request SHOULD be
   generated by a Strong Cryptographic Sequence ([RFC4086],
   Section 6.2).  TLS has a similar requirement.

   In particular, implementations should pay attention to the advance in
   [RFC4086]; see Sections 3 and, in particular, 3.4.  The random seed
   used by a device at boot MUST be unique across all devices and all
   bootstraps.  Resetting a device to factory default state does not
   obviate this requirement.

11.4.  Freshness in Voucher-Requests

   A concern has been raised that the pledge voucher-request should
   contain some content (a nonce) provided by the registrar and/or MASA
   in order for those actors to verify that the pledge voucher-request
   is fresh.

   There are a number of operational problems with getting a nonce from
   the MASA to the pledge.  It is somewhat easier to collect a random
   value from the registrar, but as the registrar is not yet vouched
   for, such a registrar nonce has little value.  There are privacy and
   logistical challenges to addressing these operational issues, so if
   such a thing were to be considered, it would have to provide some
   clear value.  This section examines the impacts of not having a fresh
   pledge voucher-request.

   Because the registrar authenticates the pledge, a full MITM attack is
   not possible, despite the provisional TLS authentication by the
   pledge (see Section 5.)  Instead, we examine the case of a fake
   registrar (Rm) that communicates with the pledge in parallel or in
   close-time proximity with the intended registrar.  (This scenario is
   intentionally supported as described in Section 4.1.)

   The fake registrar (Rm) can obtain a voucher signed by the MASA
   either directly or through arbitrary intermediaries.  Assuming that
   the MASA accepts the registrar voucher-request (because either the Rm
   is collaborating with a legitimate registrar according to supply-
   chain information or the MASA is in audit-log only mode), then a
   voucher linking the pledge to the registrar Rm is issued.

   Such a voucher, when passed back to the pledge, would link the pledge
   to registrar Rm and permit the pledge to end the provisional state.
   It now trusts the Rm and, if it has any security vulnerabilities
   leverageable by an Rm with full administrative control, can be
   assumed to be a threat against the intended registrar.

   This flow is mitigated by the intended registrar verifying the audit-
   logs available from the MASA as described in Section 5.8.  The Rm
   might chose to collect a voucher-request but wait until after the
   intended registrar completes the authorization process before
   submitting it.  This pledge voucher-request would be "stale" in that
   it has a nonce that no longer matches the internal state of the
   pledge.  In order to successfully use any resulting voucher, the Rm
   would need to remove the stale nonce or anticipate the pledge's
   future nonce state.  Reducing the possibility of this is why the
   pledge is mandated to generate a strong random or pseudo-random
   number nonce.

   Additionally, in order to successfully use the resulting voucher, the
   Rm would have to attack the pledge and return it to a bootstrapping-
   enabled state.  This would require wiping the pledge of current
   configuration and triggering a rebootstrapping of the pledge.  This
   is no more likely than simply taking control of the pledge directly,
   but if this is a consideration, it is RECOMMENDED that the target
   network take the following steps:

   *  Ongoing network monitoring for unexpected bootstrapping attempts
      by pledges.

   *  Retrieval and examination of MASA log information upon the
      occurrence of any such unexpected events.  The Rm will be listed
      in the logs along with nonce information for analysis.

11.5.  Trusting Manufacturers

   The BRSKI extensions to EST permit a new pledge to be completely
   configured with domain-specific trust anchors.  The link from built-
   in manufacturer-provided trust anchors to domain-specific trust
   anchors is mediated by the signed voucher artifact.

   If the manufacturer's IDevID signing key is not properly validated,
   then there is a risk that the network will accept a pledge that
   should not be a member of the network.  As the address of the
   manufacturer's MASA is provided in the IDevID using the extension
   from Section 2.3, the malicious pledge will have no problem
   collaborating with its MASA to produce a completely valid voucher.

   BRSKI does not, however, fundamentally change the trust model from
   domain owner to manufacturer.  Assuming that the pledge used its
   IDevID with EST [RFC7030] and BRSKI, the domain (registrar) still
   needs to trust the manufacturer.

   Establishing this trust between domain and manufacturer is outside
   the scope of BRSKI.  There are a number of mechanisms that can be
   adopted including:

   *  Manually configuring each manufacturer's trust anchor.

   *  A TOFU mechanism.  A human would be queried upon seeing a
      manufacturer's trust anchor for the first time, and then the trust
      anchor would be installed to the trusted store.  There are risks
      with this; even if the key to name mapping is validated using
      something like the WebPKI, there remains the possibility that the
      name is a look alike: e.g., dem0.example. vs.  demO.example.

   *  scanning the trust anchor from a QR code that came with the
      packaging (this is really a manual TOFU mechanism).

   *  some sales integration processing where trust anchors are provided
      as part of the sales process, probably included in a digital
      packing "slip", or a sales invoice.

   *  consortium membership, where all manufacturers of a particular
      device category (e.g, a light bulb or a cable modem) are signed by
      a CA specifically for this.  This is done by CableLabs today.  It
      is used for authentication and authorization as part of
      [docsisroot] and [TR069].

   The existing WebPKI provides a reasonable anchor between manufacturer
   name and public key.  It authenticates the key.  It does not provide
   a reasonable authorization for the manufacturer, so it is not
   directly usable on its own.

11.6.  Manufacturer Maintenance of Trust Anchors

   BRSKI depends upon the manufacturer building in trust anchors to the
   pledge device.  The voucher artifact that is signed by the MASA will
   be validated by the pledge using that anchor.  This implies that the
   manufacturer needs to maintain access to a signing key that the
   pledge can validate.

   The manufacturer will need to maintain the ability to make signatures
   that can be validated for the lifetime that the device could be
   onboarded.  Whether this onboarding lifetime is less than the device
   lifetime depends upon how the device is used.  An inventory of
   devices kept in a warehouse as spares might not be onboarded for many
   decades.

   There are good cryptographic hygiene reasons why a manufacturer would
   not want to maintain access to a private key for many decades.  A
   manufacturer in that situation can leverage a long-term CA anchor,
   built-in to the pledge, and then a certificate chain may be
   incorporated using the normal CMS certificate set.  This may increase
   the size of the voucher artifacts, but that is not a significant
   issue in non-constrained environments.

   There are a few other operational variations that manufacturers could
   consider.  For instance, there is no reason that every device need
   have the same set of trust anchors preinstalled.  Devices built in
   different factories, or on different days, or in any other
   consideration, could have different trust anchors built in, and the
   record of which batch the device is in would be recorded in the asset
   database.  The manufacturer would then know which anchor to sign an
   artifact against.

   Aside from the concern about long-term access to private keys, a
   major limiting factor for the shelf life of many devices will be the
   age of the cryptographic algorithms included.  A device produced in
   2019 will have hardware and software capable of validating algorithms
   common in 2019 and will have no defense against attacks (both quantum
   and von Neumann brute-force attacks) that have not yet been invented.
   This concern is orthogonal to the concern about access to private
   keys, but this concern likely dominates and limits the life span of a
   device in a warehouse.  If any update to the firmware to support new
   cryptographic mechanisms were possible (while the device was in a
   warehouse), updates to trust anchors would also be done at the same
   time.

   The set of standard operating procedures for maintaining high-value
   private keys is well documented.  For instance, the WebPKI provides a
   number of options for audits in [cabforumaudit], and the DNSSEC root
   operations are well documented in [dnssecroot].

   It is not clear if manufacturers will take this level of precaution,
   or how strong the economic incentives are to maintain an appropriate
   level of security.

   The next section examines the risk due to a compromised manufacturer
   IDevID signing key.  This is followed by examination of the risk due
   to a compromised MASA key.  The third section below examines the
   situation where a MASA web server itself is under attacker control,
   but the MASA signing key itself is safe in a not-directly connected
   hardware module.

11.6.1.  Compromise of Manufacturer IDevID Signing Keys

   An attacker that has access to the key that the manufacturer uses to
   sign IDevID certificates can create counterfeit devices.  Such
   devices can claim to be from a particular manufacturer but can be
   entirely different devices: Trojan horses in effect.

   As the attacker controls the MASA URL in the certificate, the
   registrar can be convinced to talk to the attacker's MASA.  The
   registrar does not need to be in any kind of promiscuous mode to be
   vulnerable.

   In addition to creating fake devices, the attacker may also be able
   to issue revocations for existing certificates if the IDevID
   certificate process relies upon CRL lists that are distributed.

   There does not otherwise seem to be any risk from this compromise to
   devices that are already deployed or that are sitting locally in
   boxes waiting for deployment (local spares).  The issue is that
   operators will be unable to trust devices that have been in an
   uncontrolled warehouse as they do not know if those are real devices.

11.6.2.  Compromise of MASA Signing Keys

   There are two periods of time in which to consider: when the MASA key
   has fallen into the hands of an attacker and after the MASA
   recognizes that the key has been compromised.

11.6.2.1.  Attacker Opportunities with a Compromised MASA Key

   An attacker that has access to the MASA signing key could create
   vouchers.  These vouchers could be for existing deployed devices or
   for devices that are still in a warehouse.  In order to exploit these
   vouchers, two things need to occur: the device has to go through a
   factory default boot cycle, and the registrar has to be convinced to
   contact the attacker's MASA.

   If the attacker controls a registrar that is visible to the device,
   then there is no difficulty in delivery of the false voucher.  A
   possible practical example of an attack like this would be in a data
   center, at an ISP peering point (whether a public IX or a private
   peering point).  In such a situation, there are already cables
   attached to the equipment that lead to other devices (the peers at
   the IX), and through those links, the false voucher could be
   delivered.  The difficult part would be to put the device through a
   factory reset.  This might be accomplished through social engineering
   of data center staff.  Most locked cages have ventilation holes, and
   possibly a long "paperclip" could reach through to depress a factory
   reset button.  Once such a piece of ISP equipment has been
   compromised, it could be used to compromise equipment that it was
   connected to (through long haul links even), assuming that those
   pieces of equipment could also be forced through a factory reset.

   The above scenario seems rather unlikely as it requires some element
   of physical access; but if there was a remote exploit that did not
   cause a direct breach, but rather a fault that resulted in a factory
   reset, this could provide a reasonable path.

   The above deals with ANI uses of BRSKI.  For cases where IEEE 802.11
   or 802.15.4 is involved, the need to connect directly to the device
   is eliminated, but the need to do a factory reset is not.  Physical
   possession of the device is not required as above, provided that
   there is some way to force a factory reset.  With some consumer
   devices that have low overall implementation quality, end users might
   be familiar with the need to reset the device regularly.

   The authors are unable to come up with an attack scenario where a
   compromised voucher signature enables an attacker to introduce a
   compromised pledge into an existing operator's network.  This is the
   case because the operator controls the communication between
   registrar and MASA, and there is no opportunity to introduce the fake
   voucher through that conduit.

11.6.2.2.  Risks after Key Compromise is Known

   Once the operator of the MASA realizes that the voucher signing key
   has been compromised, it has to do a few things.

   First, it MUST issue a firmware update to all devices that had that
   key as a trust anchor, such that they will no longer trust vouchers
   from that key.  This will affect devices in the field that are
   operating, but those devices, being in operation, are not performing
   onboarding operations, so this is not a critical patch.

   Devices in boxes (in warehouses) are vulnerable and remain vulnerable
   until patched.  An operator would be prudent to unbox the devices,
   onboard them in a safe environment, and then perform firmware
   updates.  This does not have to be done by the end-operator; it could
   be done by a distributor that stores the spares.  A recommended
   practice for high-value devices (which typically have a <4hr service
   window) may be to validate the device operation on a regular basis
   anyway.

   If the onboarding process includes attestations about firmware
   versions, then through that process, the operator would be advised to
   upgrade the firmware before going into production.  Unfortunately,
   this does not help against situations where the attacker operates
   their own registrar (as listed above).

   The need for short-lived vouchers is explained in [RFC8366],
   Section 6.1.  The nonce guarantees freshness, and the short-lived
   nature of the voucher means that the window to deliver a fake voucher
   is very short.  A nonceless, long-lived voucher would be the only
   option for the attacker, and devices in the warehouse would be
   vulnerable to such a thing.

   A key operational recommendation is for manufacturers to sign
   nonceless, long-lived vouchers with a different key than what is used
   to sign short-lived vouchers.  That key needs significantly better
   protection.  If both keys come from a common trust-anchor (the
   manufacturer's CA), then a compromise of the manufacturer's CA would
   compromise both keys.  Such a compromise of the manufacturer's CA
   likely compromises all keys outlined in this section.

11.6.3.  Compromise of MASA Web Service

   An attacker that takes over the MASA web service can inflict a number
   of attacks.  The most obvious one is simply to take the database
   listing of customers and devices and sell the data to other attackers
   who will now know where to find potentially vulnerable devices.

   The second most obvious thing that the attacker can do is to kill the
   service, or make it operate unreliably, making customers frustrated.
   This could have a serious effect on the ability to deploy new
   services by customers and would be a significant issue during
   disaster recovery.

   While the compromise of the MASA web service may lead to the
   compromise of the MASA voucher signing key, if the signing occurs
   offboard (such as in a hardware signing module (HSM)), then the key
   may well be safe, but control over it resides with the attacker.

   Such an attacker can issue vouchers for any device presently in
   service.  Said device still needs to be convinced to go through a
   factory reset process before an attack.

   If the attacker has access to a key that is trusted for long-lived
   nonceless vouchers, then they could issue vouchers for devices that
   are not yet in service.  This attack may be very hard to verify as it
   would involve doing firmware updates on every device in warehouses (a
   potentially ruinously expensive process); a manufacturer might be
   reluctant to admit this possibility.

11.7.  YANG Module Security Considerations

   As described in Section 7.4 (Security Considerations) of [RFC8366],
   the YANG module specified in this document defines the schema for
   data that is subsequently encapsulated by a CMS signed-data content
   type, as described in Section 5 of [RFC5652].  As such, all of the
   YANG-modeled data is protected from modification.

   The use of YANG to define data structures, via the "yang-data"
   statement, is relatively new and distinct from the traditional use of
   YANG to define an API accessed by network management protocols such
   as NETCONF [RFC6241] and RESTCONF [RFC8040].  For this reason, these
   guidelines do not follow the template described by Section 3.7 of
   [RFC8407].

12.  References

12.1.  Normative References

   [IDevID]   IEEE, "IEEE Standard for Local and metropolitan area
              networks - Secure Device Identity", IEEE 802.1AR,
              <https://1.ieee802.org/security/802-1ar>.

   [ITU.X690] ITU-T, "Information Technology - ASN.1 encoding rules:
              Specification of Basic Encoding Rules (BER), Canonical
              Encoding Rules (CER) and Distinguished Encoding Rules
              (DER)", ITU-T Recommendation X.690, ISO/IEC 8825-1:2015,
              August 2015, <https://www.itu.int/rec/T-REC-X.690>.

   [REST]     Fielding, R.F., "Architectural Styles and the Design of
              Network-based Software Architectures", 2000,
              <http://www.ics.uci.edu/~fielding/pubs/dissertation/
              fielding_dissertation.pdf>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <https://www.rfc-editor.org/info/rfc3339>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
              Levkowetz, Ed., "Extensible Authentication Protocol
              (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004,
              <https://www.rfc-editor.org/info/rfc3748>.

   [RFC3927]  Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
              Configuration of IPv4 Link-Local Addresses", RFC 3927,
              DOI 10.17487/RFC3927, May 2005,
              <https://www.rfc-editor.org/info/rfc3927>.

   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
              "Randomness Requirements for Security", BCP 106, RFC 4086,
              DOI 10.17487/RFC4086, June 2005,
              <https://www.rfc-editor.org/info/rfc4086>.

   [RFC4519]  Sciberras, A., Ed., "Lightweight Directory Access Protocol
              (LDAP): Schema for User Applications", RFC 4519,
              DOI 10.17487/RFC4519, June 2006,
              <https://www.rfc-editor.org/info/rfc4519>.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
              <https://www.rfc-editor.org/info/rfc4648>.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,
              <https://www.rfc-editor.org/info/rfc4862>.

   [RFC5272]  Schaad, J. and M. Myers, "Certificate Management over CMS
              (CMC)", RFC 5272, DOI 10.17487/RFC5272, June 2008,
              <https://www.rfc-editor.org/info/rfc5272>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/info/rfc5280>.

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,
              <https://www.rfc-editor.org/info/rfc5652>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
              2011, <https://www.rfc-editor.org/info/rfc6125>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6762]  Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
              DOI 10.17487/RFC6762, February 2013,
              <https://www.rfc-editor.org/info/rfc6762>.

   [RFC6763]  Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
              <https://www.rfc-editor.org/info/rfc6763>.

   [RFC7030]  Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
              "Enrollment over Secure Transport", RFC 7030,
              DOI 10.17487/RFC7030, October 2013,
              <https://www.rfc-editor.org/info/rfc7030>.

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <https://www.rfc-editor.org/info/rfc7230>.

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,
              <https://www.rfc-editor.org/info/rfc7231>.

   [RFC7469]  Evans, C., Palmer, C., and R. Sleevi, "Public Key Pinning
              Extension for HTTP", RFC 7469, DOI 10.17487/RFC7469, April
              2015, <https://www.rfc-editor.org/info/rfc7469>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <https://www.rfc-editor.org/info/rfc7951>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/info/rfc8259>.

   [RFC8366]  Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
              "A Voucher Artifact for Bootstrapping Protocols",
              RFC 8366, DOI 10.17487/RFC8366, May 2018,
              <https://www.rfc-editor.org/info/rfc8366>.

   [RFC8368]  Eckert, T., Ed. and M. Behringer, "Using an Autonomic
              Control Plane for Stable Connectivity of Network
              Operations, Administration, and Maintenance (OAM)",
              RFC 8368, DOI 10.17487/RFC8368, May 2018,
              <https://www.rfc-editor.org/info/rfc8368>.

   [RFC8407]  Bierman, A., "Guidelines for Authors and Reviewers of
              Documents Containing YANG Data Models", BCP 216, RFC 8407,
              DOI 10.17487/RFC8407, October 2018,
              <https://www.rfc-editor.org/info/rfc8407>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8610]  Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
              Definition Language (CDDL): A Notational Convention to
              Express Concise Binary Object Representation (CBOR) and
              JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
              June 2019, <https://www.rfc-editor.org/info/rfc8610>.

   [RFC8951]  Richardson, M., Werner, T., and W. Pan, "Clarification of
              Enrollment over Secure Transport (EST): Transfer Encodings
              and ASN.1", RFC 8951, DOI 10.17487/RFC8951, November 2020,
              <https://www.rfc-editor.org/info/rfc8951>.

   [RFC8981]  Gont, F., Krishnan, S., Narten, T., and R. Draves,
              "Temporary Address Extensions for Stateless Address
              Autoconfiguration in IPv6", RFC 8981,
              DOI 10.17487/RFC8981, February 2021,
              <https://www.rfc-editor.org/info/rfc8981>.

   [RFC8990]  Bormann, C., Carpenter, B., Ed., and B. Liu, Ed., "GeneRic
              Autonomic Signaling Protocol (GRASP)", RFC 8990,
              DOI 10.17487/RFC8990, May 2021,
              <https://www.rfc-editor.org/rfc/rfc8990>.

   [RFC8994]  Eckert, T., Ed., Behringer, M., Ed., and S. Bjarnason, "An
              Autonomic Control Plane (ACP)", RFC 8994,
              DOI 10.17487/RFC8994, May 2021,
              <https://www.rfc-editor.org/rfc/rfc8994>.

12.2.  Informative References

   [ACE-COAP-EST]
              van der Stok, P., Kampanakis, P., Richardson, M., and S.
              Raza, "EST over secure CoAP (EST-coaps)", Work in
              Progress, Internet-Draft, draft-ietf-ace-coap-est-18, 6
              January 2020,
              <https://tools.ietf.org/html/draft-ietf-ace-coap-est-18>.

   [ANIMA-CONSTRAINED-VOUCHER]
              Richardson, M., van der Stok, P., Kampanakis, P., and E.
              Dijk, "Constrained Voucher Artifacts for Bootstrapping
              Protocols", Work in Progress, Internet-Draft, draft-ietf-
              anima-constrained-voucher-10, 21 February 2021,
              <https://tools.ietf.org/html/draft-ietf-anima-constrained-
              voucher-10>.

   [ANIMA-STATE]
              Richardson, M., "Considerations for stateful vs stateless
              join router in ANIMA bootstrap", Work in Progress,
              Internet-Draft, draft-richardson-anima-state-for-
              joinrouter-03, 22 September 2020,
              <https://tools.ietf.org/html/draft-richardson-anima-state-
              for-joinrouter-03>.

   [brewski]  Urban Dictionary, "brewski", March 2003,
              <https://www.urbandictionary.com/define.php?term=brewski>.

   [cabforumaudit]
              CA/Browser Forum, "Information for Auditors and
              Assessors", August 2019, <https://cabforum.org/
              information-for-auditors-and-assessors/>.

   [Dingledine]
              Dingledine, R., Mathewson, N., and P. Syverson, "Tor: The
              Second-Generation Onion Router", August 2004,
              <https://svn-archive.torproject.org/svn/projects/design-
              paper/tor-design.pdf>.

   [dnssecroot]
              "DNSSEC Practice Statement for the Root Zone ZSK
              Operator", December 2017,
              <https://www.iana.org/dnssec/procedures/zsk-operator/dps-
              zsk-operator-v2.1.pdf>.

   [docsisroot]
              "CableLabs Digital Certificate Issuance Service", February
              2018, <https://www.cablelabs.com/resources/digital-
              certificate-issuance-service/>.

   [imprinting]
              Wikipedia, "Imprinting (psychology)", January 2021,
              <https://en.wikipedia.org/w/
              index.php?title=Imprinting_(psychology)&=999211441>.

   [IoTstrangeThings]
              ESET, "IoT of toys stranger than fiction: Cybersecurity
              and data privacy update", March 2017,
              <https://www.welivesecurity.com/2017/03/03/internet-of-
              things-security-privacy-iot-update/>.

   [livingwithIoT]
              Silicon Republic, "What is it actually like to live in a
              house filled with IoT devices?", February 2018,
              <https://www.siliconrepublic.com/machines/iot-smart-
              devices-reality>.

   [minerva]  Richardson, M., "Minerva reference implementation for
              BRSKI", 2020, <https://minerva.sandelman.ca/>.

   [minervagithub]
              "ANIMA Minerva toolkit",
              <https://github.com/ANIMAgus-minerva>.

   [openssl]  OpenSSL, "OpenSSL X509 Utility", September 2019,
              <https://www.openssl.org/docs/man1.1.1/man1/openssl-
              x509.html/>.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, DOI 10.17487/RFC2131, March 1997,
              <https://www.rfc-editor.org/info/rfc2131>.

   [RFC2663]  Srisuresh, P. and M. Holdrege, "IP Network Address
              Translator (NAT) Terminology and Considerations",
              RFC 2663, DOI 10.17487/RFC2663, August 1999,
              <https://www.rfc-editor.org/info/rfc2663>.

   [RFC5209]  Sangster, P., Khosravi, H., Mani, M., Narayan, K., and J.
              Tardo, "Network Endpoint Assessment (NEA): Overview and
              Requirements", RFC 5209, DOI 10.17487/RFC5209, June 2008,
              <https://www.rfc-editor.org/info/rfc5209>.

   [RFC6960]  Santesson, S., Myers, M., Ankney, R., Malpani, A.,
              Galperin, S., and C. Adams, "X.509 Internet Public Key
              Infrastructure Online Certificate Status Protocol - OCSP",
              RFC 6960, DOI 10.17487/RFC6960, June 2013,
              <https://www.rfc-editor.org/info/rfc6960>.

   [RFC6961]  Pettersen, Y., "The Transport Layer Security (TLS)
              Multiple Certificate Status Request Extension", RFC 6961,
              DOI 10.17487/RFC6961, June 2013,
              <https://www.rfc-editor.org/info/rfc6961>.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,
              <https://www.rfc-editor.org/info/rfc7228>.

   [RFC7258]  Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
              Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
              2014, <https://www.rfc-editor.org/info/rfc7258>.

   [RFC7435]  Dukhovni, V., "Opportunistic Security: Some Protection
              Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
              December 2014, <https://www.rfc-editor.org/info/rfc7435>.

   [RFC7575]  Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
              Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
              Networking: Definitions and Design Goals", RFC 7575,
              DOI 10.17487/RFC7575, June 2015,
              <https://www.rfc-editor.org/info/rfc7575>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [RFC8615]  Nottingham, M., "Well-Known Uniform Resource Identifiers
              (URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019,
              <https://www.rfc-editor.org/info/rfc8615>.

   [RFC8993]  Behringer, M., Ed., Carpenter, B., Eckert, T., Ciavaglia,
              L., and J. Nobre, "A Reference Model for Autonomic
              Networking", RFC 8993, DOI 10.17487/RFC8993, May 2021,
              <https://www.rfc-editor.org/info/rfc8993>.

   [slowloris]
              Wikipedia, "Slowloris (computer security)", January 2021,
              <https://en.wikipedia.org/w/index.php?title=Slowloris_(com
              puter_security)&oldid=1001473290/>.

   [softwareescrow]
              Wikipedia, "Source code escrow", March 2020,
              <https://en.wikipedia.org/w/
              index.php?title=Source_code_escrow&oldid=948073074>.

   [Stajano99theresurrecting]
              Stajano, F. and R. Anderson, "The Resurrecting Duckling:
              Security Issues for Ad-hoc Wireless Networks", 1999,
              <https://www.cl.cam.ac.uk/~fms27/papers/1999-StajanoAnd-
              duckling.pdf>.

   [TR069]    Broadband Forum, "CPE WAN Management Protocol", TR-069,
              Issue 1, Amendment 6, March 2018, <https://www.broadband-
              forum.org/download/TR-069_Amendment-6.pdf>.

   [W3C.capability-urls]
              Tennison, J., "Good Practices for Capability URLs", W3C
              First Public Working Draft, World Wide Web Consortium WD 
              WD-capability-urls-20140218, February 2014,
              <https://www.w3.org/TR/2014/WD-capability-urls>.

   [YANG-KEYSTORE]
              Watsen, K., "A YANG Data Model for a Keystore", Work in
              Progress, Internet-Draft, draft-ietf-netconf-keystore-22,
              18 May 2021, <https://tools.ietf.org/html/draft-ietf-
              netconf-keystore-22>.

Appendix A.  IPv4 and Non-ANI Operations

   The specification of BRSKI in Section 4 intentionally covers only the
   mechanisms for an IPv6 pledge using link-local addresses.  This
   section describes non-normative extensions that can be used in other
   environments.

A.1.  IPv4 Link-Local Addresses

   Instead of an IPv6 link-local address, an IPv4 address may be
   generated using "Dynamic Configuration of IPv4 Link-Local Addresses"
   [RFC3927].

   In the case where an IPv4 link-local address is formed, the bootstrap
   process would continue, as in an IPv6 case, by looking for a
   (circuit) proxy.

A.2.  Use of DHCPv4

   The pledge MAY obtain an IP address via DHCP ([RFC2131].  The DHCP-
   provided parameters for the Domain Name System can be used to perform
   DNS operations if all local discovery attempts fail.

Appendix B.  mDNS / DNS-SD Proxy Discovery Options

   Pledge discovery of the proxy (Section 4.1) MAY be performed with
   DNS-based Service Discovery [RFC6763] over Multicast DNS [RFC6762] to
   discover the proxy at "_brski-proxy._tcp.local.".

   Proxy discovery of the registrar (Section 4.3) MAY be performed with
   DNS-based Service Discovery over Multicast DNS to discover registrars
   by searching for the service "_brski-registrar._tcp.local.".

   To prevent unacceptable levels of network traffic, when using mDNS,
   the congestion avoidance mechanisms specified in [RFC6762], Section 7
   MUST be followed.  The pledge SHOULD listen for an unsolicited
   broadcast response as described in [RFC6762].  This allows devices to
   avoid announcing their presence via mDNS broadcasts and instead
   silently join a network by watching for periodic unsolicited
   broadcast responses.

   Discovery of the registrar MAY also be performed with DNS-based
   Service Discovery by searching for the service "_brski-
   registrar._tcp.example.com".  In this case, the domain "example.com"
   is discovered as described in [RFC6763], Section 11 (Appendix A.2 of
   this document suggests the use of DHCP parameters).

   If no local proxy or registrar service is located using the GRASP
   mechanisms or the above-mentioned DNS-based Service Discovery
   methods, the pledge MAY contact a well-known manufacturer-provided
   bootstrapping server by performing a DNS lookup using a well-known
   URI such as "brski-registrar.manufacturer.example.com".  The details
   of the URI are manufacturer specific.  Manufacturers that leverage
   this method on the pledge are responsible for providing the registrar
   service.  Also see Section 2.7.

   The current DNS services returned during each query are maintained
   until bootstrapping is completed.  If bootstrapping fails and the
   pledge returns to the Discovery state, it picks up where it left off
   and continues attempting bootstrapping.  For example, if the first
   Multicast DNS _bootstrapks._tcp.local response doesn't work, then the
   second and third responses are tried.  If these fail, the pledge
   moves on to normal DNS-based Service Discovery.

Appendix C.  Example Vouchers

   Three entities are involved in a voucher: the MASA issues (signs) it,
   the registrar's public key is mentioned in it, and the pledge
   validates it.  In order to provide reproducible examples, the public
   and private keys for an example MASA and registrar are listed first.

   The keys come from an open source reference implementation of BRSKI,
   called "Minerva" [minerva].  It is available on GitHub
   [minervagithub].  The keys presented here are used in the unit and
   integration tests.  The MASA code is called "highway", the registrar
   code is called "fountain", and the example client is called "reach".

   The public key components of each are presented as base64
   certificates and are decoded by openssl's x509 utility so that the
   extensions can be seen.  This was version 1.1.1c of the library and
   utility of [openssl].

C.1.  Keys Involved

   The manufacturer has a CA that signs the pledge's IDevID.  In
   addition, the Manufacturer's signing authority (the MASA) signs the
   vouchers, and that certificate must distributed to the devices at
   manufacturing time so that vouchers can be validated.

C.1.1.  Manufacturer Certification Authority for IDevID Signatures

   This private key is the CA that signs IDevID certificates:

   <CODE BEGINS> file "vendor.key"
   -----BEGIN EC PRIVATE KEY-----
   MIGkAgEBBDCAYkoLW1IEA5SKKhMMdkTK7sJxk5ybKqYq9Yr5aR7tNwqXyLGS7z8G
   8S4w/UJ58BqgBwYFK4EEACKhZANiAAQu5/yktJbFLjMC87h7b+yTreFuF8GwewKH
   L4mS0r0dVAQubqDUQcTrjvpXrXCpTojiLCzgp8fzkcUDkZ9LD/M90LDipiLNIOkP
   juF8QkoAbT8pMrY83MS8y76wZ7AalNQ=
   -----END EC PRIVATE KEY-----
   <CODE ENDS>

   This public key validates IDevID certificates:

   file: examples/vendor.key

   <CODE BEGINS> file "vendor.cert"
   Certificate:
       Data:
           Version: 3 (0x2)
           Serial Number: 1216069925 (0x487bc125)
           Signature Algorithm: ecdsa-with-SHA256
           Issuer: CN = highway-test.example.com CA
           Validity
               Not Before: Apr 13 20:34:24 2021 GMT
               Not After : Apr 13 20:34:24 2023 GMT
           Subject: CN = highway-test.example.com CA
           Subject Public Key Info:
               Public Key Algorithm: id-ecPublicKey
                   Public-Key: (384 bit)
                   pub:
                       04:2e:e7:fc:a4:b4:96:c5:2e:33:02:f3:b8:7b:6f:
                       ec:93:ad:e1:6e:17:c1:b0:7b:02:87:2f:89:92:d2:
                       bd:1d:54:04:2e:6e:a0:d4:41:c4:eb:8e:fa:57:ad:
                       70:a9:4e:88:e2:2c:2c:e0:a7:c7:f3:91:c5:03:91:
                       9f:4b:0f:f3:3d:d0:b0:e2:a6:22:cd:20:e9:0f:8e:
                       e1:7c:42:4a:00:6d:3f:29:32:b6:3c:dc:c4:bc:cb:
                       be:b0:67:b0:1a:94:d4
                   ASN1 OID: secp384r1
                   NIST CURVE: P-384
           X509v3 extensions:
               X509v3 Basic Constraints: critical
                   CA:TRUE
               X509v3 Key Usage: critical
                   Certificate Sign, CRL Sign
               X509v3 Subject Key Identifier:
                   5E:0C:A9:52:5A:8C:DF:A9:0F:03:14:E9:96:F1:80:76:
                   8C:53:8A:08
               X509v3 Authority Key Identifier:
                   keyid:5E:0C:A9:52:5A:8C:DF:A9:0F:03:14:E9:96:F1:
                   80:76:8C:53:8A:08

       Signature Algorithm: ecdsa-with-SHA256
            30:64:02:30:60:37:a0:66:89:80:27:e1:0d:e5:43:9a:62:f1:
            02:bc:0f:72:6d:a9:e9:cb:84:a5:c6:44:d3:41:9e:5d:ce:7d:
            46:16:6e:15:de:f7:cc:e8:3e:61:f9:03:7c:20:c4:b7:02:30:
            7f:e9:f3:12:bb:06:c6:24:00:2b:41:aa:21:6b:d8:25:ed:81:
            07:11:ef:66:8f:06:bf:c8:be:f0:58:74:24:45:39:4d:04:fc:
            31:69:6f:cf:db:fe:61:7b:c3:24:31:ff
   -----BEGIN CERTIFICATE-----
   MIIB3TCCAWSgAwIBAgIESHvBJTAKBggqhkjOPQQDAjAmMSQwIgYDVQQDDBtoaWdo
   d2F5LXRlc3QuZXhhbXBsZS5jb20gQ0EwHhcNMjEwNDEzMjAzNDI0WhcNMjMwNDEz
   MjAzNDI0WjAmMSQwIgYDVQQDDBtoaWdod2F5LXRlc3QuZXhhbXBsZS5jb20gQ0Ew
   djAQBgcqhkjOPQIBBgUrgQQAIgNiAAQu5/yktJbFLjMC87h7b+yTreFuF8GwewKH
   L4mS0r0dVAQubqDUQcTrjvpXrXCpTojiLCzgp8fzkcUDkZ9LD/M90LDipiLNIOkP
   juF8QkoAbT8pMrY83MS8y76wZ7AalNSjYzBhMA8GA1UdEwEB/wQFMAMBAf8wDgYD
   VR0PAQH/BAQDAgEGMB0GA1UdDgQWBBReDKlSWozfqQ8DFOmW8YB2jFOKCDAfBgNV
   HSMEGDAWgBReDKlSWozfqQ8DFOmW8YB2jFOKCDAKBggqhkjOPQQDAgNnADBkAjBg
   N6BmiYAn4Q3lQ5pi8QK8D3JtqenLhKXGRNNBnl3OfUYWbhXe98zoPmH5A3wgxLcC
   MH/p8xK7BsYkACtBqiFr2CXtgQcR72aPBr/IvvBYdCRFOU0E/DFpb8/b/mF7wyQx
   /w==
   -----END CERTIFICATE-----
   <CODE ENDS>

C.1.2.  MASA Key Pair for Voucher Signatures

   The MASA is the Manufacturer Authorized Signing Authority.  This key
   pair signs vouchers.  An example TLS certificate (see Section 5.4)
   HTTP authentication is not provided as it is a common form.

   This private key signs the vouchers that are presented below:

   <CODE BEGINS> file "masa.key"
   -----BEGIN EC PRIVATE KEY-----
   MHcCAQEEIFhdd0eDdzip67kXx72K+KHGJQYJHNy8pkiLJ6CcvxMGoAoGCCqGSM49
   AwEHoUQDQgAEqgQVo0S54kT4yfkbBxumdHOcHrpsqbOpMKmiMln3oB1HAW25MJV+
   gqi4tMFfSJ0iEwt8kszfWXK4rLgJS2mnpQ==
   -----END EC PRIVATE KEY-----
   <CODE ENDS>

   This public key validates vouchers, and it has been signed by the CA
   above:

   file: examples/masa.key

   <CODE BEGINS> file "masa.cert"
   Certificate:
       Data:
           Version: 3 (0x2)
           Serial Number: 193399345 (0xb870a31)
           Signature Algorithm: ecdsa-with-SHA256
           Issuer: CN = highway-test.example.com CA
           Validity
               Not Before: Apr 13 21:40:16 2021 GMT
               Not After : Apr 13 21:40:16 2023 GMT
           Subject: CN = highway-test.example.com MASA
           Subject Public Key Info:
               Public Key Algorithm: id-ecPublicKey
                   Public-Key: (256 bit)
                   pub:
                       04:aa:04:15:a3:44:b9:e2:44:f8:c9:f9:1b:07:1b:
                       a6:74:73:9c:1e:ba:6c:a9:b3:a9:30:a9:a2:32:59:
                       f7:a0:1d:47:01:6d:b9:30:95:7e:82:a8:b8:b4:c1:
                       5f:48:9d:22:13:0b:7c:92:cc:df:59:72:b8:ac:b8:
                       09:4b:69:a7:a5
                   ASN1 OID: prime256v1
                   NIST CURVE: P-256
           X509v3 extensions:
               X509v3 Basic Constraints: critical
                   CA:FALSE
       Signature Algorithm: ecdsa-with-SHA256
            30:66:02:31:00:ae:cb:61:2d:d4:5c:8d:6e:86:aa:0b:06:1d:
            c6:d3:60:ba:32:73:36:25:d3:23:85:49:87:1c:ce:94:23:79:
            1a:9e:41:55:24:1d:15:22:a1:48:bb:0a:c0:ab:3c:13:73:02:
            31:00:86:3c:67:b3:95:a2:e2:e5:f9:ad:f9:1d:9c:c1:34:32:
            78:f5:cf:ea:d5:47:03:9f:00:bf:d0:59:cb:51:c2:98:04:81:
            24:8a:51:13:50:b1:75:b2:2f:9d:a8:b4:f4:b9
   -----BEGIN CERTIFICATE-----
   MIIBcDCB9qADAgECAgQLhwoxMAoGCCqGSM49BAMCMCYxJDAiBgNVBAMMG2hpZ2h3
   YXktdGVzdC5leGFtcGxlLmNvbSBDQTAeFw0yMTA0MTMyMTQwMTZaFw0yMzA0MTMy
   MTQwMTZaMCgxJjAkBgNVBAMMHWhpZ2h3YXktdGVzdC5leGFtcGxlLmNvbSBNQVNB
   MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEqgQVo0S54kT4yfkbBxumdHOcHrps
   qbOpMKmiMln3oB1HAW25MJV+gqi4tMFfSJ0iEwt8kszfWXK4rLgJS2mnpaMQMA4w
   DAYDVR0TAQH/BAIwADAKBggqhkjOPQQDAgNpADBmAjEArsthLdRcjW6GqgsGHcbT
   YLoyczYl0yOFSYcczpQjeRqeQVUkHRUioUi7CsCrPBNzAjEAhjxns5Wi4uX5rfkd
   nME0Mnj1z+rVRwOfAL/QWctRwpgEgSSKURNQsXWyL52otPS5
   -----END CERTIFICATE-----
   <CODE ENDS>

C.1.3.  Registrar Certification Authority

   This CA enrolls the pledge once it is authorized, and it also signs
   the registrar's certificate.

   <CODE BEGINS> file "ownerca_secp384r1.key"
   -----BEGIN EC PRIVATE KEY-----
   MIGkAgEBBDCHnLI0MSOLf8XndiZqoZdqblcPR5YSoPGhPOuFxWy1gFi9HbWv8b/R
   EGdRgGEVSjKgBwYFK4EEACKhZANiAAQbf1m6F8MavGaNjGzgw/oxcQ9l9iKRvbdW
   gAfb37h6pUVNeYpGlxlZljGxj2l9Mr48yD5bY7VG9qjVb5v5wPPTuRQ/ckdRpHbd
   0vC/9cqPMAF/+MJf0/UgA0SLi/IHbLQ=
   -----END EC PRIVATE KEY-----
   <CODE ENDS>

   The public key is indicated in a pledge voucher-request to show
   proximity.

   file: examples/ownerca_secp384r1.key

   <CODE BEGINS> file "ownerca_secp384r1.cert"
   Certificate:
       Data:
           Version: 3 (0x2)
           Serial Number: 694879833 (0x296b0659)
           Signature Algorithm: ecdsa-with-SHA256
           Issuer: DC = ca, DC = sandelman,
            CN = fountain-test.example.com Unstrung Fountain Root CA
           Validity
               Not Before: Feb 25 21:31:45 2020 GMT
               Not After : Feb 24 21:31:45 2022 GMT
           Subject: DC = ca, DC = sandelman,
            CN = fountain-test.example.com Unstrung Fountain Root CA
           Subject Public Key Info:
               Public Key Algorithm: id-ecPublicKey
                   Public-Key: (384 bit)
                   pub:
                       04:1b:7f:59:ba:17:c3:1a:bc:66:8d:8c:6c:e0:c3:
                       fa:31:71:0f:65:f6:22:91:bd:b7:56:80:07:db:df:
                       b8:7a:a5:45:4d:79:8a:46:97:19:59:96:31:b1:8f:
                       69:7d:32:be:3c:c8:3e:5b:63:b5:46:f6:a8:d5:6f:
                       9b:f9:c0:f3:d3:b9:14:3f:72:47:51:a4:76:dd:d2:
                       f0:bf:f5:ca:8f:30:01:7f:f8:c2:5f:d3:f5:20:03:
                       44:8b:8b:f2:07:6c:b4
                   ASN1 OID: secp384r1
                   NIST CURVE: P-384
           X509v3 extensions:
               X509v3 Basic Constraints: critical
                   CA:TRUE
               X509v3 Key Usage: critical
                   Certificate Sign, CRL Sign
               X509v3 Subject Key Identifier:
                   B9:A5:F6:CB:11:E1:07:A4:49:2C:A7:08:C6:7C:10:BC:
                   87:B3:74:26
               X509v3 Authority Key Identifier:
                   keyid:B9:A5:F6:CB:11:E1:07:A4:49:2C:A7:08:C6:7C:
                   10:BC:87:B3:74:26

       Signature Algorithm: ecdsa-with-SHA256
            30:64:02:30:20:83:06:ce:8d:98:a4:54:7a:66:4c:4a:3a:70:
            c2:52:36:5a:52:8d:59:7d:20:9b:2a:69:14:58:87:38:d8:55:
            79:dd:fd:29:38:95:1e:91:93:76:b4:f5:66:29:44:b4:02:30:
            6f:38:f9:af:12:ed:30:d5:85:29:7c:b1:16:58:bd:67:91:43:
            c4:0d:30:f9:d8:1c:ac:2f:06:dd:bc:d5:06:42:2c:84:a2:04:
            ea:02:a4:5f:17:51:26:fb:d9:2f:d2:5c
   -----BEGIN CERTIFICATE-----
   MIICazCCAfKgAwIBAgIEKWsGWTAKBggqhkjOPQQDAjBtMRIwEAYKCZImiZPyLGQB
   GRYCY2ExGTAXBgoJkiaJk/IsZAEZFglzYW5kZWxtYW4xPDA6BgNVBAMMM2ZvdW50
   YWluLXRlc3QuZXhhbXBsZS5jb20gVW5zdHJ1bmcgRm91bnRhaW4gUm9vdCBDQTAe
   Fw0yMDAyMjUyMTMxNDVaFw0yMjAyMjQyMTMxNDVaMG0xEjAQBgoJkiaJk/IsZAEZ
   FgJjYTEZMBcGCgmSJomT8ixkARkWCXNhbmRlbG1hbjE8MDoGA1UEAwwzZm91bnRh
   aW4tdGVzdC5leGFtcGxlLmNvbSBVbnN0cnVuZyBGb3VudGFpbiBSb290IENBMHYw
   EAYHKoZIzj0CAQYFK4EEACIDYgAEG39ZuhfDGrxmjYxs4MP6MXEPZfYikb23VoAH
   29+4eqVFTXmKRpcZWZYxsY9pfTK+PMg+W2O1Rvao1W+b+cDz07kUP3JHUaR23dLw
   v/XKjzABf/jCX9P1IANEi4vyB2y0o2MwYTAPBgNVHRMBAf8EBTADAQH/MA4GA1Ud
   DwEB/wQEAwIBBjAdBgNVHQ4EFgQUuaX2yxHhB6RJLKcIxnwQvIezdCYwHwYDVR0j
   BBgwFoAUuaX2yxHhB6RJLKcIxnwQvIezdCYwCgYIKoZIzj0EAwIDZwAwZAIwIIMG
   zo2YpFR6ZkxKOnDCUjZaUo1ZfSCbKmkUWIc42FV53f0pOJUekZN2tPVmKUS0AjBv
   OPmvEu0w1YUpfLEWWL1nkUPEDTD52BysLwbdvNUGQiyEogTqAqRfF1Em+9kv0lw=
   -----END CERTIFICATE-----
   <CODE ENDS>

C.1.4.  Registrar Key Pair

   The registrar is the representative of the domain owner.  This key
   signs registrar voucher-requests and terminates the TLS connection
   from the pledge.

   <CODE BEGINS> file "jrc_prime256v1.key"
   -----BEGIN EC PRIVATE KEY-----
   MHcCAQEEIFZodk+PC5Mu24+ra0sbOjKzan+dW5rvDAR7YuJUOC1YoAoGCCqGSM49
   AwEHoUQDQgAElmVQcjS6n+Xd5l/28IFv6UiegQwSBztGj5dkK2MAjQIPV8l8lH+E
   jLIOYdbJiI0VtEIf1/Jqt+TOBfinTNOLOg==
   -----END EC PRIVATE KEY-----
   <CODE ENDS>

   The public key is indicated in a pledge voucher-request to show
   proximity.

   <CODE BEGINS> file "jrc_prime256v1.cert"
   Certificate:
       Data:
           Version: 3 (0x2)
           Serial Number: 1066965842 (0x3f989b52)
           Signature Algorithm: ecdsa-with-SHA256
           Issuer: DC = ca, DC = sandelman,
            CN = fountain-test.example.com Unstrung Fountain Root CA
           Validity
               Not Before: Feb 25 21:31:54 2020 GMT
               Not After : Feb 24 21:31:54 2022 GMT
           Subject: DC = ca, DC = sandelman,
            CN = fountain-test.example.com
           Subject Public Key Info:
               Public Key Algorithm: id-ecPublicKey
                   Public-Key: (256 bit)
                   pub:
                       04:96:65:50:72:34:ba:9f:e5:dd:e6:5f:f6:f0:81:
                       6f:e9:48:9e:81:0c:12:07:3b:46:8f:97:64:2b:63:
                       00:8d:02:0f:57:c9:7c:94:7f:84:8c:b2:0e:61:d6:
                       c9:88:8d:15:b4:42:1f:d7:f2:6a:b7:e4:ce:05:f8:
                       a7:4c:d3:8b:3a
                   ASN1 OID: prime256v1
                   NIST CURVE: P-256
           X509v3 extensions:
               X509v3 Extended Key Usage: critical
                   CMC Registration Authority
               X509v3 Key Usage: critical
                   Digital Signature
       Signature Algorithm: ecdsa-with-SHA256
            30:65:02:30:66:4f:60:4c:55:48:1e:96:07:f8:dd:1f:b9:c8:
            12:8d:45:36:87:9b:23:c0:bc:bb:f1:cb:3d:26:15:56:6f:5f:
            1f:bf:d5:1c:0e:6a:09:af:1b:76:97:99:19:23:fd:7e:02:31:
            00:bc:ac:c3:41:b0:ba:0d:af:52:f9:9c:6e:7a:7f:00:1d:23:
            c8:62:01:61:bc:4b:c5:c0:47:99:35:0a:0c:77:61:44:01:4a:
            07:52:70:57:00:75:ff:be:07:0e:98:cb:e5
   -----BEGIN CERTIFICATE-----
   MIIB/DCCAYKgAwIBAgIEP5ibUjAKBggqhkjOPQQDAjBtMRIwEAYKCZImiZPyLGQB
   GRYCY2ExGTAXBgoJkiaJk/IsZAEZFglzYW5kZWxtYW4xPDA6BgNVBAMMM2ZvdW50
   YWluLXRlc3QuZXhhbXBsZS5jb20gVW5zdHJ1bmcgRm91bnRhaW4gUm9vdCBDQTAe
   Fw0yMDAyMjUyMTMxNTRaFw0yMjAyMjQyMTMxNTRaMFMxEjAQBgoJkiaJk/IsZAEZ
   FgJjYTEZMBcGCgmSJomT8ixkARkWCXNhbmRlbG1hbjEiMCAGA1UEAwwZZm91bnRh
   aW4tdGVzdC5leGFtcGxlLmNvbTBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABJZl
   UHI0up/l3eZf9vCBb+lInoEMEgc7Ro+XZCtjAI0CD1fJfJR/hIyyDmHWyYiNFbRC
   H9fyarfkzgX4p0zTizqjKjAoMBYGA1UdJQEB/wQMMAoGCCsGAQUFBwMcMA4GA1Ud
   DwEB/wQEAwIHgDAKBggqhkjOPQQDAgNoADBlAjBmT2BMVUgelgf43R+5yBKNRTaH
   myPAvLvxyz0mFVZvXx+/1RwOagmvG3aXmRkj/X4CMQC8rMNBsLoNr1L5nG56fwAd
   I8hiAWG8S8XAR5k1Cgx3YUQBSgdScFcAdf++Bw6Yy+U=
   -----END CERTIFICATE-----
   <CODE ENDS>

C.1.5.  Pledge Key Pair

   The pledge has an IDevID key pair built in at manufacturing time:

   <CODE BEGINS> file "idevid_00-D0-E5-F2-00-02.key"
   -----BEGIN EC PRIVATE KEY-----
   MHcCAQEEIBHNh6r8QRevRuo+tEmBJeFjQKf6bpFA/9NGoltv+9sNoAoGCCqGSM49
   AwEHoUQDQgAEA6N1Q4ezfMAKmoecrfb0OBMc1AyEH+BATkF58FsTSyBxs0SbSWLx
   FjDOuwB9gLGn2TsTUJumJ6VPw5Z/TP4hJw==
   -----END EC PRIVATE KEY-----
   <CODE ENDS>

   The certificate is used by the registrar to find the MASA.

   <CODE BEGINS> file "idevid_00-D0-E5-F2-00-02.cert"
   Certificate:
       Data:
           Version: 3 (0x2)
           Serial Number: 521731815 (0x1f18fee7)
           Signature Algorithm: ecdsa-with-SHA256
           Issuer: CN = highway-test.example.com CA
           Validity
               Not Before: Apr 27 18:29:30 2021 GMT
               Not After : Dec 31 00:00:00 2999 GMT
           Subject: serialNumber = 00-D0-E5-F2-00-02
           Subject Public Key Info:
               Public Key Algorithm: id-ecPublicKey
                   Public-Key: (256 bit)
                   pub:
                       04:03:a3:75:43:87:b3:7c:c0:0a:9a:87:9c:ad:f6:
                       f4:38:13:1c:d4:0c:84:1f:e0:40:4e:41:79:f0:5b:
                       13:4b:20:71:b3:44:9b:49:62:f1:16:30:ce:bb:00:
                       7d:80:b1:a7:d9:3b:13:50:9b:a6:27:a5:4f:c3:96:
                       7f:4c:fe:21:27
                   ASN1 OID: prime256v1
                   NIST CURVE: P-256
           X509v3 extensions:
               X509v3 Subject Key Identifier:
                   45:88:CC:96:96:00:64:37:B0:BA:23:65:64:64:54:08:
                   06:6C:56:AD
               X509v3 Basic Constraints:
                   CA:FALSE
               1.3.6.1.5.5.7.1.32:
                   ..highway-test.example.com:9443
       Signature Algorithm: ecdsa-with-SHA256
            30:65:02:30:62:2a:db:be:34:f7:1b:cb:85:de:26:8e:43:00:
            f9:0d:88:c8:77:a8:dd:3c:08:40:54:bc:ec:3d:b6:dc:70:2b:
            c3:7f:ca:19:21:9a:a0:ab:c5:51:8e:aa:df:36:de:8b:02:31:
            00:b2:5d:59:f8:47:c7:ed:03:97:a8:c0:c7:a8:81:fa:a8:86:
            ed:67:64:37:51:7a:6e:9c:a3:82:4d:6d:ad:bc:f3:35:9e:9d:
            6a:a2:6d:7f:7f:25:1c:03:ef:f0:ba:9b:71
   -----BEGIN CERTIFICATE-----
   MIIBrzCCATWgAwIBAgIEHxj+5zAKBggqhkjOPQQDAjAmMSQwIgYDVQQDDBtoaWdo
   d2F5LXRlc3QuZXhhbXBsZS5jb20gQ0EwIBcNMjEwNDI3MTgyOTMwWhgPMjk5OTEy
   MzEwMDAwMDBaMBwxGjAYBgNVBAUTETAwLUQwLUU1LUYyLTAwLTAyMFkwEwYHKoZI
   zj0CAQYIKoZIzj0DAQcDQgAEA6N1Q4ezfMAKmoecrfb0OBMc1AyEH+BATkF58FsT
   SyBxs0SbSWLxFjDOuwB9gLGn2TsTUJumJ6VPw5Z/TP4hJ6NZMFcwHQYDVR0OBBYE
   FEWIzJaWAGQ3sLojZWRkVAgGbFatMAkGA1UdEwQCMAAwKwYIKwYBBQUHASAEHxYd
   aGlnaHdheS10ZXN0LmV4YW1wbGUuY29tOjk0NDMwCgYIKoZIzj0EAwIDaAAwZQIw
   YirbvjT3G8uF3iaOQwD5DYjId6jdPAhAVLzsPbbccCvDf8oZIZqgq8VRjqrfNt6L
   AjEAsl1Z+EfH7QOXqMDHqIH6qIbtZ2Q3UXpunKOCTW2tvPM1np1qom1/fyUcA+/w
   uptx
   -----END CERTIFICATE-----
   <CODE ENDS>

C.2.  Example Process

   The JSON examples below are wrapped at 60 columns.  This results in
   strings that have newlines in them, which makes them invalid JSON as
   is.  The strings would otherwise be too long, so they need to be
   unwrapped before processing.

   For readability, the output of the asn1parse has been truncated at 68
   columns rather than wrapped.

C.2.1.  Pledge to Registrar

   As described in Section 5.2, the pledge will sign a pledge voucher-
   request containing the registrar's public key in the proximity-
   registrar-cert field.  The base64 has been wrapped at 60 characters
   for presentation reasons.

   <CODE BEGINS> file "vr_00-D0-E5-F2-00-02.b64"
   MIIGcAYJKoZIhvcNAQcCoIIGYTCCBl0CAQExDTALBglghkgBZQMEAgEwggOJBgkqhkiG
   9w0BBwGgggN6BIIDdnsiaWV0Zi12b3VjaGVyLXJlcXVlc3Q6dm91Y2hlciI6eyJhc3Nl
   cnRpb24iOiJwcm94aW1pdHkiLCJjcmVhdGVkLW9uIjoiMjAyMS0wNC0xM1QxNzo0Mzoy
   My43NDctMDQ6MDAiLCJzZXJpYWwtbnVtYmVyIjoiMDAtRDAtRTUtRjItMDAtMDIiLCJu
   b25jZSI6Ii1fWEU5eks5cThMbDFxeWxNdExLZWciLCJwcm94aW1pdHktcmVnaXN0cmFy
   LWNlcnQiOiJNSUlCL0RDQ0FZS2dBd0lCQWdJRVA1aWJVakFLQmdncWhrak9QUVFEQWpC
   dE1SSXdFQVlLQ1pJbWlaUHlMR1FCR1JZQ1kyRXhHVEFYQmdvSmtpYUprL0lzWkFFWkZn
   bHpZVzVrWld4dFlXNHhQREE2QmdOVkJBTU1NMlp2ZFc1MFlXbHVMWFJsYzNRdVpYaGhi
   WEJzWlM1amIyMGdWVzV6ZEhKMWJtY2dSbTkxYm5SaGFXNGdVbTl2ZENCRFFUQWVGdzB5
   TURBeU1qVXlNVE14TlRSYUZ3MHlNakF5TWpReU1UTXhOVFJhTUZNeEVqQVFCZ29Ka2lh
   SmsvSXNaQUVaRmdKallURVpNQmNHQ2dtU0pvbVQ4aXhrQVJrV0NYTmhibVJsYkcxaGJq
   RWlNQ0FHQTFVRUF3d1pabTkxYm5SaGFXNHRkR1Z6ZEM1bGVHRnRjR3hsTG1OdmJUQlpN
   Qk1HQnlxR1NNNDlBZ0VHQ0NxR1NNNDlBd0VIQTBJQUJKWmxVSEkwdXAvbDNlWmY5dkNC
   YitsSW5vRU1FZ2M3Um8rWFpDdGpBSTBDRDFmSmZKUi9oSXl5RG1IV3lZaU5GYlJDSDlm
   eWFyZmt6Z1g0cDB6VGl6cWpLakFvTUJZR0ExVWRKUUVCL3dRTU1Bb0dDQ3NHQVFVRkJ3
   TWNNQTRHQTFVZER3RUIvd1FFQXdJSGdEQUtCZ2dxaGtqT1BRUURBZ05vQURCbEFqQm1U
   MkJNVlVnZWxnZjQzUis1eUJLTlJUYUhteVBBdkx2eHl6MG1GVlp2WHgrLzFSd09hZ212
   RzNhWG1Sa2ovWDRDTVFDOHJNTkJzTG9OcjFMNW5HNTZmd0FkSThoaUFXRzhTOFhBUjVr
   MUNneDNZVVFCU2dkU2NGY0FkZisrQnc2WXkrVT0ifX2gggGyMIIBrjCCATWgAwIBAgIE
   DYOv2TAKBggqhkjOPQQDAjAmMSQwIgYDVQQDDBtoaWdod2F5LXRlc3QuZXhhbXBsZS5j
   b20gQ0EwIBcNMjEwNDEzMjAzNzM5WhgPMjk5OTEyMzEwMDAwMDBaMBwxGjAYBgNVBAUM
   ETAwLUQwLUU1LUYyLTAwLTAyMFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEA6N1Q4ez
   fMAKmoecrfb0OBMc1AyEH+BATkF58FsTSyBxs0SbSWLxFjDOuwB9gLGn2TsTUJumJ6VP
   w5Z/TP4hJ6NZMFcwHQYDVR0OBBYEFEWIzJaWAGQ3sLojZWRkVAgGbFatMAkGA1UdEwQC
   MAAwKwYIKwYBBQUHASAEHxYdaGlnaHdheS10ZXN0LmV4YW1wbGUuY29tOjk0NDMwCgYI
   KoZIzj0EAwIDZwAwZAIwTmlG8sXkKGNbwbKQcYMapFbmSbnHHURFUoFuRqvbgYX7FlXp
   BczfwF2kllNuujigAjAow1kc4r55EmiH+OMEXjBNlWlBSZC5QuJjEf0Jsmxssc+pucjO
   J4ShqnexMEy7bjAxggEEMIIBAAIBATAuMCYxJDAiBgNVBAMMG2hpZ2h3YXktdGVzdC5l
   eGFtcGxlLmNvbSBDQQIEDYOv2TALBglghkgBZQMEAgGgaTAYBgkqhkiG9w0BCQMxCwYJ
   KoZIhvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0yMTA0MTMyMTQzMjNaMC8GCSqGSIb3DQEJ
   BDEiBCBJwhyYibIjeqeR3bOaLURzMlGrc3F2X+kvJ1errtoCtTAKBggqhkjOPQQDAgRH
   MEUCIQCmYuCE61HFQXH/E16GDOCsVquDtgr+Q/6/Du/9QkzA7gIgf7MFhAIPW2PNwRa2
   vZFQAKXUbimkiHKzXBA8md0VHbU=
   <CODE ENDS>

   The ASN1 decoding of the artifact:

   file: examples/vr_00-D0-E5-F2-00-02.b64

    0:d=0  hl=4 l=1648 cons: SEQUENCE
    4:d=1  hl=2 l=   9 prim: OBJECT            :pkcs7-signedData
   15:d=1  hl=4 l=1633 cons: cont [ 0 ]
   19:d=2  hl=4 l=1629 cons: SEQUENCE
   23:d=3  hl=2 l=   1 prim: INTEGER           :01
   26:d=3  hl=2 l=  13 cons: SET
   28:d=4  hl=2 l=  11 cons: SEQUENCE
   30:d=5  hl=2 l=   9 prim: OBJECT            :sha256
   41:d=3  hl=4 l= 905 cons: SEQUENCE
   45:d=4  hl=2 l=   9 prim: OBJECT            :pkcs7-data
   56:d=4  hl=4 l= 890 cons: cont [ 0 ]
   60:d=5  hl=4 l= 886 prim: OCTET STRING      :{"ietf-voucher-request:v
  950:d=3  hl=4 l= 434 cons: cont [ 0 ]
  954:d=4  hl=4 l= 430 cons: SEQUENCE
  958:d=5  hl=4 l= 309 cons: SEQUENCE
  962:d=6  hl=2 l=   3 cons: cont [ 0 ]
  964:d=7  hl=2 l=   1 prim: INTEGER           :02
  967:d=6  hl=2 l=   4 prim: INTEGER           :0D83AFD9
  973:d=6  hl=2 l=  10 cons: SEQUENCE
  975:d=7  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
  985:d=6  hl=2 l=  38 cons: SEQUENCE
  987:d=7  hl=2 l=  36 cons: SET
  989:d=8  hl=2 l=  34 cons: SEQUENCE
  991:d=9  hl=2 l=   3 prim: OBJECT            :commonName
  996:d=9  hl=2 l=  27 prim: UTF8STRING        :highway-test.example.com
 1025:d=6  hl=2 l=  32 cons: SEQUENCE
 1027:d=7  hl=2 l=  13 prim: UTCTIME           :210413203739Z
 1042:d=7  hl=2 l=  15 prim: GENERALIZEDTIME   :29991231000000Z
 1059:d=6  hl=2 l=  28 cons: SEQUENCE
 1061:d=7  hl=2 l=  26 cons: SET
 1063:d=8  hl=2 l=  24 cons: SEQUENCE
 1065:d=9  hl=2 l=   3 prim: OBJECT            :serialNumber
 1070:d=9  hl=2 l=  17 prim: UTF8STRING        :00-D0-E5-F2-00-02
 1089:d=6  hl=2 l=  89 cons: SEQUENCE
 1091:d=7  hl=2 l=  19 cons: SEQUENCE
 1093:d=8  hl=2 l=   7 prim: OBJECT            :id-ecPublicKey
 1102:d=8  hl=2 l=   8 prim: OBJECT            :prime256v1
 1112:d=7  hl=2 l=  66 prim: BIT STRING
 1180:d=6  hl=2 l=  89 cons: cont [ 3 ]
 1182:d=7  hl=2 l=  87 cons: SEQUENCE
 1184:d=8  hl=2 l=  29 cons: SEQUENCE
 1186:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Subject Key Ident
 1191:d=9  hl=2 l=  22 prim: OCTET STRING      [HEX DUMP]:04144588CC9696
 1215:d=8  hl=2 l=   9 cons: SEQUENCE
 1217:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Basic Constraints
 1222:d=9  hl=2 l=   2 prim: OCTET STRING      [HEX DUMP]:3000
 1226:d=8  hl=2 l=  43 cons: SEQUENCE
 1228:d=9  hl=2 l=   8 prim: OBJECT            :1.3.6.1.5.5.7.1.32
 1238:d=9  hl=2 l=  31 prim: OCTET STRING      [HEX DUMP]:161D6869676877
 1271:d=5  hl=2 l=  10 cons: SEQUENCE
 1273:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 1283:d=5  hl=2 l= 103 prim: BIT STRING
 1388:d=3  hl=4 l= 260 cons: SET
 1392:d=4  hl=4 l= 256 cons: SEQUENCE
 1396:d=5  hl=2 l=   1 prim: INTEGER           :01
 1399:d=5  hl=2 l=  46 cons: SEQUENCE
 1401:d=6  hl=2 l=  38 cons: SEQUENCE
 1403:d=7  hl=2 l=  36 cons: SET
 1405:d=8  hl=2 l=  34 cons: SEQUENCE
 1407:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 1412:d=9  hl=2 l=  27 prim: UTF8STRING        :highway-test.example.com
 1441:d=6  hl=2 l=   4 prim: INTEGER           :0D83AFD9
 1447:d=5  hl=2 l=  11 cons: SEQUENCE
 1449:d=6  hl=2 l=   9 prim: OBJECT            :sha256
 1460:d=5  hl=2 l= 105 cons: cont [ 0 ]
 1462:d=6  hl=2 l=  24 cons: SEQUENCE
 1464:d=7  hl=2 l=   9 prim: OBJECT            :contentType
 1475:d=7  hl=2 l=  11 cons: SET
 1477:d=8  hl=2 l=   9 prim: OBJECT            :pkcs7-data
 1488:d=6  hl=2 l=  28 cons: SEQUENCE
 1490:d=7  hl=2 l=   9 prim: OBJECT            :signingTime
 1501:d=7  hl=2 l=  15 cons: SET
 1503:d=8  hl=2 l=  13 prim: UTCTIME           :210413214323Z
 1518:d=6  hl=2 l=  47 cons: SEQUENCE
 1520:d=7  hl=2 l=   9 prim: OBJECT            :messageDigest
 1531:d=7  hl=2 l=  34 cons: SET
 1533:d=8  hl=2 l=  32 prim: OCTET STRING      [HEX DUMP]:49C21C9889B223
 1567:d=5  hl=2 l=  10 cons: SEQUENCE
 1569:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 1579:d=5  hl=2 l=  71 prim: OCTET STRING      [HEX DUMP]:3045022100A662

   The JSON contained in the voucher-request:

   {"ietf-voucher-request:voucher":{"assertion":"proximity","cr
   eated-on":"2021-04-13T17:43:23.747-04:00","serial-number":"0
   0-D0-E5-F2-00-02","nonce":"-_XE9zK9q8Ll1qylMtLKeg","proximit
   y-registrar-cert":"MIIB/DCCAYKgAwIBAgIEP5ibUjAKBggqhkjOPQQDA
   jBtMRIwEAYKCZImiZPyLGQBGRYCY2ExGTAXBgoJkiaJk/IsZAEZFglzYW5kZ
   WxtYW4xPDA6BgNVBAMMM2ZvdW50YWluLXRlc3QuZXhhbXBsZS5jb20gVW5zd
   HJ1bmcgRm91bnRhaW4gUm9vdCBDQTAeFw0yMDAyMjUyMTMxNTRaFw0yMjAyM
   jQyMTMxNTRaMFMxEjAQBgoJkiaJk/IsZAEZFgJjYTEZMBcGCgmSJomT8ixkA
   RkWCXNhbmRlbG1hbjEiMCAGA1UEAwwZZm91bnRhaW4tdGVzdC5leGFtcGxlL
   mNvbTBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABJZlUHI0up/l3eZf9vCBb
   +lInoEMEgc7Ro+XZCtjAI0CD1fJfJR/hIyyDmHWyYiNFbRCH9fyarfkzgX4p
   0zTizqjKjAoMBYGA1UdJQEB/wQMMAoGCCsGAQUFBwMcMA4GA1UdDwEB/wQEA
   wIHgDAKBggqhkjOPQQDAgNoADBlAjBmT2BMVUgelgf43R+5yBKNRTaHmyPAv
   Lvxyz0mFVZvXx+/1RwOagmvG3aXmRkj/X4CMQC8rMNBsLoNr1L5nG56fwAdI
   8hiAWG8S8XAR5k1Cgx3YUQBSgdScFcAdf++Bw6Yy+U="}}

C.2.2.  Registrar to MASA

   As described in Section 5.5, the registrar will sign a registrar
   voucher-request and will include the pledge's voucher-request in the
   prior-signed-voucher-request.

   <CODE BEGINS> file "parboiled_vr_00-D0-E5-F2-00-02.b64"
   MIIPYwYJKoZIhvcNAQcCoIIPVDCCD1ACAQExDTALBglghkgBZQMEAgEwggl4BgkqhkiG
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   ZWxtYW4xPDA6BgNVBAMMM2ZvdW50YWluLXRlc3QuZXhhbXBsZS5jb20gVW5zdHJ1bmcg
   Rm91bnRhaW4gUm9vdCBDQTAeFw0yMDAyMjUyMTMxNDVaFw0yMjAyMjQyMTMxNDVaMG0x
   EjAQBgoJkiaJk/IsZAEZFgJjYTEZMBcGCgmSJomT8ixkARkWCXNhbmRlbG1hbjE8MDoG
   A1UEAwwzZm91bnRhaW4tdGVzdC5leGFtcGxlLmNvbSBVbnN0cnVuZyBGb3VudGFpbiBS
   b290IENBMHYwEAYHKoZIzj0CAQYFK4EEACIDYgAEG39ZuhfDGrxmjYxs4MP6MXEPZfYi
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   3dLwv/XKjzABf/jCX9P1IANEi4vyB2y0o2MwYTAPBgNVHRMBAf8EBTADAQH/MA4GA1Ud
   DwEB/wQEAwIBBjAdBgNVHQ4EFgQUuaX2yxHhB6RJLKcIxnwQvIezdCYwHwYDVR0jBBgw
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   ZkxKOnDCUjZaUo1ZfSCbKmkUWIc42FV53f0pOJUekZN2tPVmKUS0AjBvOPmvEu0w1YUp
   fLEWWL1nkUPEDTD52BysLwbdvNUGQiyEogTqAqRfF1Em+9kv0lwxggFLMIIBRwIBATB1
   MG0xEjAQBgoJkiaJk/IsZAEZFgJjYTEZMBcGCgmSJomT8ixkARkWCXNhbmRlbG1hbjE8
   MDoGA1UEAwwzZm91bnRhaW4tdGVzdC5leGFtcGxlLmNvbSBVbnN0cnVuZyBGb3VudGFp
   biBSb290IENBAgQ/mJtSMAsGCWCGSAFlAwQCAaBpMBgGCSqGSIb3DQEJAzELBgkqhkiG
   9w0BBwEwHAYJKoZIhvcNAQkFMQ8XDTIxMDQxMzIxNDMyM1owLwYJKoZIhvcNAQkEMSIE
   IEnOrdWjlG70K74IhCJ7UXi+wPS+r2C8DFEqjabGP+G8MAoGCCqGSM49BAMCBEcwRQIh
   AMhO3M+tSWb2wKTBOXPArN+XvjSzAhaQA/uLj3qhPwi/AiBDDthf6mjMuirqXE0yjMif
   C2UY9oNUFF9Nl0wEQpBBAA==
   <CODE ENDS>

   The ASN1 decoding of the artifact:

   file: examples/parboiled_vr_00_D0-E5-02-00-2D.b64

    0:d=0  hl=4 l=3939 cons: SEQUENCE
    4:d=1  hl=2 l=   9 prim: OBJECT            :pkcs7-signedData
   15:d=1  hl=4 l=3924 cons: cont [ 0 ]
   19:d=2  hl=4 l=3920 cons: SEQUENCE
   23:d=3  hl=2 l=   1 prim: INTEGER           :01
   26:d=3  hl=2 l=  13 cons: SET
   28:d=4  hl=2 l=  11 cons: SEQUENCE
   30:d=5  hl=2 l=   9 prim: OBJECT            :sha256
   41:d=3  hl=4 l=2424 cons: SEQUENCE
   45:d=4  hl=2 l=   9 prim: OBJECT            :pkcs7-data
   56:d=4  hl=4 l=2409 cons: cont [ 0 ]
   60:d=5  hl=4 l=2405 prim: OCTET STRING      :{"ietf-voucher-request:v
 2469:d=3  hl=4 l=1135 cons: cont [ 0 ]
 2473:d=4  hl=4 l= 508 cons: SEQUENCE
 2477:d=5  hl=4 l= 386 cons: SEQUENCE
 2481:d=6  hl=2 l=   3 cons: cont [ 0 ]
 2483:d=7  hl=2 l=   1 prim: INTEGER           :02
 2486:d=6  hl=2 l=   4 prim: INTEGER           :3F989B52
 2492:d=6  hl=2 l=  10 cons: SEQUENCE
 2494:d=7  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 2504:d=6  hl=2 l= 109 cons: SEQUENCE
 2506:d=7  hl=2 l=  18 cons: SET
 2508:d=8  hl=2 l=  16 cons: SEQUENCE
 2510:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 2522:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 2526:d=7  hl=2 l=  25 cons: SET
 2528:d=8  hl=2 l=  23 cons: SEQUENCE
 2530:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 2542:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 2553:d=7  hl=2 l=  60 cons: SET
 2555:d=8  hl=2 l=  58 cons: SEQUENCE
 2557:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 2562:d=9  hl=2 l=  51 prim: UTF8STRING        :fountain-test.example.co
 2615:d=6  hl=2 l=  30 cons: SEQUENCE
 2617:d=7  hl=2 l=  13 prim: UTCTIME           :200225213154Z
 2632:d=7  hl=2 l=  13 prim: UTCTIME           :220224213154Z
 2647:d=6  hl=2 l=  83 cons: SEQUENCE
 2649:d=7  hl=2 l=  18 cons: SET
 2651:d=8  hl=2 l=  16 cons: SEQUENCE
 2653:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 2665:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 2669:d=7  hl=2 l=  25 cons: SET
 2671:d=8  hl=2 l=  23 cons: SEQUENCE
 2673:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 2685:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 2696:d=7  hl=2 l=  34 cons: SET
 2698:d=8  hl=2 l=  32 cons: SEQUENCE
 2700:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 2705:d=9  hl=2 l=  25 prim: UTF8STRING        :fountain-test.example.co
 2732:d=6  hl=2 l=  89 cons: SEQUENCE
 2734:d=7  hl=2 l=  19 cons: SEQUENCE
 2736:d=8  hl=2 l=   7 prim: OBJECT            :id-ecPublicKey
 2745:d=8  hl=2 l=   8 prim: OBJECT            :prime256v1
 2755:d=7  hl=2 l=  66 prim: BIT STRING
 2823:d=6  hl=2 l=  42 cons: cont [ 3 ]
 2825:d=7  hl=2 l=  40 cons: SEQUENCE
 2827:d=8  hl=2 l=  22 cons: SEQUENCE
 2829:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Extended Key Usag
 2834:d=9  hl=2 l=   1 prim: BOOLEAN           :255
 2837:d=9  hl=2 l=  12 prim: OCTET STRING      [HEX DUMP]:300A06082B0601
 2851:d=8  hl=2 l=  14 cons: SEQUENCE
 2853:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Key Usage
 2858:d=9  hl=2 l=   1 prim: BOOLEAN           :255
 2861:d=9  hl=2 l=   4 prim: OCTET STRING      [HEX DUMP]:03020780
 2867:d=5  hl=2 l=  10 cons: SEQUENCE
 2869:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 2879:d=5  hl=2 l= 104 prim: BIT STRING
 2985:d=4  hl=4 l= 619 cons: SEQUENCE
 2989:d=5  hl=4 l= 498 cons: SEQUENCE
 2993:d=6  hl=2 l=   3 cons: cont [ 0 ]
 2995:d=7  hl=2 l=   1 prim: INTEGER           :02
 2998:d=6  hl=2 l=   4 prim: INTEGER           :296B0659
 3004:d=6  hl=2 l=  10 cons: SEQUENCE
 3006:d=7  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 3016:d=6  hl=2 l= 109 cons: SEQUENCE
 3018:d=7  hl=2 l=  18 cons: SET
 3020:d=8  hl=2 l=  16 cons: SEQUENCE
 3022:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3034:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 3038:d=7  hl=2 l=  25 cons: SET
 3040:d=8  hl=2 l=  23 cons: SEQUENCE
 3042:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3054:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 3065:d=7  hl=2 l=  60 cons: SET
 3067:d=8  hl=2 l=  58 cons: SEQUENCE
 3069:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 3074:d=9  hl=2 l=  51 prim: UTF8STRING        :fountain-test.example.co
 3127:d=6  hl=2 l=  30 cons: SEQUENCE
 3129:d=7  hl=2 l=  13 prim: UTCTIME           :200225213145Z
 3144:d=7  hl=2 l=  13 prim: UTCTIME           :220224213145Z
 3159:d=6  hl=2 l= 109 cons: SEQUENCE
 3161:d=7  hl=2 l=  18 cons: SET
 3163:d=8  hl=2 l=  16 cons: SEQUENCE
 3165:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3177:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 3181:d=7  hl=2 l=  25 cons: SET
 3183:d=8  hl=2 l=  23 cons: SEQUENCE
 3185:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3197:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 3208:d=7  hl=2 l=  60 cons: SET
 3210:d=8  hl=2 l=  58 cons: SEQUENCE
 3212:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 3217:d=9  hl=2 l=  51 prim: UTF8STRING        :fountain-test.example.co
 3270:d=6  hl=2 l= 118 cons: SEQUENCE
 3272:d=7  hl=2 l=  16 cons: SEQUENCE
 3274:d=8  hl=2 l=   7 prim: OBJECT            :id-ecPublicKey
 3283:d=8  hl=2 l=   5 prim: OBJECT            :secp384r1
 3290:d=7  hl=2 l=  98 prim: BIT STRING
 3390:d=6  hl=2 l=  99 cons: cont [ 3 ]
 3392:d=7  hl=2 l=  97 cons: SEQUENCE
 3394:d=8  hl=2 l=  15 cons: SEQUENCE
 3396:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Basic Constraints
 3401:d=9  hl=2 l=   1 prim: BOOLEAN           :255
 3404:d=9  hl=2 l=   5 prim: OCTET STRING      [HEX DUMP]:30030101FF
 3411:d=8  hl=2 l=  14 cons: SEQUENCE
 3413:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Key Usage
 3418:d=9  hl=2 l=   1 prim: BOOLEAN           :255
 3421:d=9  hl=2 l=   4 prim: OCTET STRING      [HEX DUMP]:03020106
 3427:d=8  hl=2 l=  29 cons: SEQUENCE
 3429:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Subject Key Ident
 3434:d=9  hl=2 l=  22 prim: OCTET STRING      [HEX DUMP]:0414B9A5F6CB11
 3458:d=8  hl=2 l=  31 cons: SEQUENCE
 3460:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Authority Key Ide
 3465:d=9  hl=2 l=  24 prim: OCTET STRING      [HEX DUMP]:30168014B9A5F6
 3491:d=5  hl=2 l=  10 cons: SEQUENCE
 3493:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 3503:d=5  hl=2 l= 103 prim: BIT STRING
 3608:d=3  hl=4 l= 331 cons: SET
 3612:d=4  hl=4 l= 327 cons: SEQUENCE
 3616:d=5  hl=2 l=   1 prim: INTEGER           :01
 3619:d=5  hl=2 l= 117 cons: SEQUENCE
 3621:d=6  hl=2 l= 109 cons: SEQUENCE
 3623:d=7  hl=2 l=  18 cons: SET
 3625:d=8  hl=2 l=  16 cons: SEQUENCE
 3627:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3639:d=9  hl=2 l=   2 prim: IA5STRING         :ca
 3643:d=7  hl=2 l=  25 cons: SET
 3645:d=8  hl=2 l=  23 cons: SEQUENCE
 3647:d=9  hl=2 l=  10 prim: OBJECT            :domainComponent
 3659:d=9  hl=2 l=   9 prim: IA5STRING         :sandelman
 3670:d=7  hl=2 l=  60 cons: SET
 3672:d=8  hl=2 l=  58 cons: SEQUENCE
 3674:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 3679:d=9  hl=2 l=  51 prim: UTF8STRING        :fountain-test.example.co
 3732:d=6  hl=2 l=   4 prim: INTEGER           :3F989B52
 3738:d=5  hl=2 l=  11 cons: SEQUENCE
 3740:d=6  hl=2 l=   9 prim: OBJECT            :sha256
 3751:d=5  hl=2 l= 105 cons: cont [ 0 ]
 3753:d=6  hl=2 l=  24 cons: SEQUENCE
 3755:d=7  hl=2 l=   9 prim: OBJECT            :contentType
 3766:d=7  hl=2 l=  11 cons: SET
 3768:d=8  hl=2 l=   9 prim: OBJECT            :pkcs7-data
 3779:d=6  hl=2 l=  28 cons: SEQUENCE
 3781:d=7  hl=2 l=   9 prim: OBJECT            :signingTime
 3792:d=7  hl=2 l=  15 cons: SET
 3794:d=8  hl=2 l=  13 prim: UTCTIME           :210413214323Z
 3809:d=6  hl=2 l=  47 cons: SEQUENCE
 3811:d=7  hl=2 l=   9 prim: OBJECT            :messageDigest
 3822:d=7  hl=2 l=  34 cons: SET
 3824:d=8  hl=2 l=  32 prim: OCTET STRING      [HEX DUMP]:49CEADD5A3946E
 3858:d=5  hl=2 l=  10 cons: SEQUENCE
 3860:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 3870:d=5  hl=2 l=  71 prim: OCTET STRING      [HEX DUMP]:3045022100C84E

   The JSON contained in the voucher-request.  Note that the previous
   voucher-request is in the prior-signed-voucher-request attribute.

   {"ietf-voucher-request:voucher":{"assertion":"proximity","cr
   eated-on":"2021-04-13T21:43:23.787Z","serial-number":"00-D0-
   E5-F2-00-02","nonce":"-_XE9zK9q8Ll1qylMtLKeg","prior-signed-
   voucher-request":"MIIGcAYJKoZIhvcNAQcCoIIGYTCCBl0CAQExDTALBg
   lghkgBZQMEAgEwggOJBgkqhkiG9w0BBwGgggN6BIIDdnsiaWV0Zi12b3VjaG
   VyLXJlcXVlc3Q6dm91Y2hlciI6eyJhc3NlcnRpb24iOiJwcm94aW1pdHkiLC
   JjcmVhdGVkLW9uIjoiMjAyMS0wNC0xM1QxNzo0MzoyMy43NDctMDQ6MDAiLC
   JzZXJpYWwtbnVtYmVyIjoiMDAtRDAtRTUtRjItMDAtMDIiLCJub25jZSI6Ii
   1fWEU5eks5cThMbDFxeWxNdExLZWciLCJwcm94aW1pdHktcmVnaXN0cmFyLW
   NlcnQiOiJNSUlCL0RDQ0FZS2dBd0lCQWdJRVA1aWJVakFLQmdncWhrak9QUV
   FEQWpCdE1SSXdFQVlLQ1pJbWlaUHlMR1FCR1JZQ1kyRXhHVEFYQmdvSmtpYU
   prL0lzWkFFWkZnbHpZVzVrWld4dFlXNHhQREE2QmdOVkJBTU1NMlp2ZFc1MF
   lXbHVMWFJsYzNRdVpYaGhiWEJzWlM1amIyMGdWVzV6ZEhKMWJtY2dSbTkxYm
   5SaGFXNGdVbTl2ZENCRFFUQWVGdzB5TURBeU1qVXlNVE14TlRSYUZ3MHlNak
   F5TWpReU1UTXhOVFJhTUZNeEVqQVFCZ29Ka2lhSmsvSXNaQUVaRmdKallURV
   pNQmNHQ2dtU0pvbVQ4aXhrQVJrV0NYTmhibVJsYkcxaGJqRWlNQ0FHQTFVRU
   F3d1pabTkxYm5SaGFXNHRkR1Z6ZEM1bGVHRnRjR3hsTG1OdmJUQlpNQk1HQn
   lxR1NNNDlBZ0VHQ0NxR1NNNDlBd0VIQTBJQUJKWmxVSEkwdXAvbDNlWmY5dk
   NCYitsSW5vRU1FZ2M3Um8rWFpDdGpBSTBDRDFmSmZKUi9oSXl5RG1IV3lZaU
   5GYlJDSDlmeWFyZmt6Z1g0cDB6VGl6cWpLakFvTUJZR0ExVWRKUUVCL3dRTU
   1Bb0dDQ3NHQVFVRkJ3TWNNQTRHQTFVZER3RUIvd1FFQXdJSGdEQUtCZ2dxaG
   tqT1BRUURBZ05vQURCbEFqQm1UMkJNVlVnZWxnZjQzUis1eUJLTlJUYUhteV
   BBdkx2eHl6MG1GVlp2WHgrLzFSd09hZ212RzNhWG1Sa2ovWDRDTVFDOHJNTk
   JzTG9OcjFMNW5HNTZmd0FkSThoaUFXRzhTOFhBUjVrMUNneDNZVVFCU2dkU2
   NGY0FkZisrQnc2WXkrVT0ifX2gggGyMIIBrjCCATWgAwIBAgIEDYOv2TAKBg
   gqhkjOPQQDAjAmMSQwIgYDVQQDDBtoaWdod2F5LXRlc3QuZXhhbXBsZS5jb2
   0gQ0EwIBcNMjEwNDEzMjAzNzM5WhgPMjk5OTEyMzEwMDAwMDBaMBwxGjAYBg
   NVBAUMETAwLUQwLUU1LUYyLTAwLTAyMFkwEwYHKoZIzj0CAQYIKoZIzj0DAQ
   cDQgAEA6N1Q4ezfMAKmoecrfb0OBMc1AyEH+BATkF58FsTSyBxs0SbSWLxFj
   DOuwB9gLGn2TsTUJumJ6VPw5Z/TP4hJ6NZMFcwHQYDVR0OBBYEFEWIzJaWAG
   Q3sLojZWRkVAgGbFatMAkGA1UdEwQCMAAwKwYIKwYBBQUHASAEHxYdaGlnaH
   dheS10ZXN0LmV4YW1wbGUuY29tOjk0NDMwCgYIKoZIzj0EAwIDZwAwZAIwTm
   lG8sXkKGNbwbKQcYMapFbmSbnHHURFUoFuRqvbgYX7FlXpBczfwF2kllNuuj
   igAjAow1kc4r55EmiH+OMEXjBNlWlBSZC5QuJjEf0Jsmxssc+pucjOJ4Shqn
   exMEy7bjAxggEEMIIBAAIBATAuMCYxJDAiBgNVBAMMG2hpZ2h3YXktdGVzdC
   5leGFtcGxlLmNvbSBDQQIEDYOv2TALBglghkgBZQMEAgGgaTAYBgkqhkiG9w
   0BCQMxCwYJKoZIhvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0yMTA0MTMyMTQzMj
   NaMC8GCSqGSIb3DQEJBDEiBCBJwhyYibIjeqeR3bOaLURzMlGrc3F2X+kvJ1
   errtoCtTAKBggqhkjOPQQDAgRHMEUCIQCmYuCE61HFQXH/E16GDOCsVquDtg
   r+Q/6/Du/9QkzA7gIgf7MFhAIPW2PNwRa2vZFQAKXUbimkiHKzXBA8md0VHb
   U="}}

C.2.3.  MASA to Registrar

   The MASA will return a voucher to the registrar, which is to be
   relayed to the pledge.

   <CODE BEGINS> file "voucher_00-D0-E5-F2-00-02.b64"
   MIIGIgYJKoZIhvcNAQcCoIIGEzCCBg8CAQExDTALBglghkgBZQMEAgEwggN4BgkqhkiG
   9w0BBwGgggNpBIIDZXsiaWV0Zi12b3VjaGVyOnZvdWNoZXIiOnsiYXNzZXJ0aW9uIjoi
   bG9nZ2VkIiwiY3JlYXRlZC1vbiI6IjIwMjEtMDQtMTNUMTc6NDM6MjQuNTg5LTA0OjAw
   Iiwic2VyaWFsLW51bWJlciI6IjAwLUQwLUU1LUYyLTAwLTAyIiwibm9uY2UiOiItX1hF
   OXpLOXE4TGwxcXlsTXRMS2VnIiwicGlubmVkLWRvbWFpbi1jZXJ0IjoiTUlJQi9EQ0NB
   WUtnQXdJQkFnSUVQNWliVWpBS0JnZ3Foa2pPUFFRREFqQnRNUkl3RUFZS0NaSW1pWlB5
   TEdRQkdSWUNZMkV4R1RBWEJnb0praWFKay9Jc1pBRVpGZ2x6WVc1a1pXeHRZVzR4UERB
   NkJnTlZCQU1NTTJadmRXNTBZV2x1TFhSbGMzUXVaWGhoYlhCc1pTNWpiMjBnVlc1emRI
   SjFibWNnUm05MWJuUmhhVzRnVW05dmRDQkRRVEFlRncweU1EQXlNalV5TVRNeE5UUmFG
   dzB5TWpBeU1qUXlNVE14TlRSYU1GTXhFakFRQmdvSmtpYUprL0lzWkFFWkZnSmpZVEVa
   TUJjR0NnbVNKb21UOGl4a0FSa1dDWE5oYm1SbGJHMWhiakVpTUNBR0ExVUVBd3daWm05
   MWJuUmhhVzR0ZEdWemRDNWxlR0Z0Y0d4bExtTnZiVEJaTUJNR0J5cUdTTTQ5QWdFR0ND
   cUdTTTQ5QXdFSEEwSUFCSlpsVUhJMHVwL2wzZVpmOXZDQmIrbElub0VNRWdjN1JvK1ha
   Q3RqQUkwQ0QxZkpmSlIvaEl5eURtSFd5WWlORmJSQ0g5ZnlhcmZremdYNHAwelRpenFq
   S2pBb01CWUdBMVVkSlFFQi93UU1NQW9HQ0NzR0FRVUZCd01jTUE0R0ExVWREd0VCL3dR
   RUF3SUhnREFLQmdncWhrak9QUVFEQWdOb0FEQmxBakJtVDJCTVZVZ2VsZ2Y0M1IrNXlC
   S05SVGFIbXlQQXZMdnh5ejBtRlZadlh4Ky8xUndPYWdtdkczYVhtUmtqL1g0Q01RQzhy
   TU5Cc0xvTnIxTDVuRzU2ZndBZEk4aGlBV0c4UzhYQVI1azFDZ3gzWVVRQlNnZFNjRmNB
   ZGYrK0J3Nll5K1U9In19oIIBdDCCAXAwgfagAwIBAgIEC4cKMTAKBggqhkjOPQQDAjAm
   MSQwIgYDVQQDDBtoaWdod2F5LXRlc3QuZXhhbXBsZS5jb20gQ0EwHhcNMjEwNDEzMjE0
   MDE2WhcNMjMwNDEzMjE0MDE2WjAoMSYwJAYDVQQDDB1oaWdod2F5LXRlc3QuZXhhbXBs
   ZS5jb20gTUFTQTBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABKoEFaNEueJE+Mn5Gwcb
   pnRznB66bKmzqTCpojJZ96AdRwFtuTCVfoKouLTBX0idIhMLfJLM31lyuKy4CUtpp6Wj
   EDAOMAwGA1UdEwEB/wQCMAAwCgYIKoZIzj0EAwIDaQAwZgIxAK7LYS3UXI1uhqoLBh3G
   02C6MnM2JdMjhUmHHM6UI3kankFVJB0VIqFIuwrAqzwTcwIxAIY8Z7OVouLl+a35HZzB
   NDJ49c/q1UcDnwC/0FnLUcKYBIEkilETULF1si+dqLT0uTGCAQUwggEBAgEBMC4wJjEk
   MCIGA1UEAwwbaGlnaHdheS10ZXN0LmV4YW1wbGUuY29tIENBAgQLhwoxMAsGCWCGSAFl
   AwQCAaBpMBgGCSqGSIb3DQEJAzELBgkqhkiG9w0BBwEwHAYJKoZIhvcNAQkFMQ8XDTIx
   MDQxMzIxNDMyNFowLwYJKoZIhvcNAQkEMSIEIFUUjg4WYVO+MpX122Qfk/7zm/G6/B59
   HD/xrVR0lGIjMAoGCCqGSM49BAMCBEgwRgIhAOhUfxbH2dwpB2BrTDcsYSjRkCCk/WE6
   Mdt+y4z5KD9IAiEAphwdIUb40A0noNIUpH7N2lTyAFZgyn1lNHTteY9DmYI=
   <CODE ENDS>

   The ASN1 decoding of the artifact:

   file: examples/voucher_00-D0-E5-F2-00-02.b64

    0:d=0  hl=4 l=1570 cons: SEQUENCE
    4:d=1  hl=2 l=   9 prim: OBJECT            :pkcs7-signedData
   15:d=1  hl=4 l=1555 cons: cont [ 0 ]
   19:d=2  hl=4 l=1551 cons: SEQUENCE
   23:d=3  hl=2 l=   1 prim: INTEGER           :01
   26:d=3  hl=2 l=  13 cons: SET
   28:d=4  hl=2 l=  11 cons: SEQUENCE
   30:d=5  hl=2 l=   9 prim: OBJECT            :sha256
   41:d=3  hl=4 l= 888 cons: SEQUENCE
   45:d=4  hl=2 l=   9 prim: OBJECT            :pkcs7-data
   56:d=4  hl=4 l= 873 cons: cont [ 0 ]
   60:d=5  hl=4 l= 869 prim: OCTET STRING      :{"ietf-voucher:voucher":
  933:d=3  hl=4 l= 372 cons: cont [ 0 ]
  937:d=4  hl=4 l= 368 cons: SEQUENCE
  941:d=5  hl=3 l= 246 cons: SEQUENCE
  944:d=6  hl=2 l=   3 cons: cont [ 0 ]
  946:d=7  hl=2 l=   1 prim: INTEGER           :02
  949:d=6  hl=2 l=   4 prim: INTEGER           :0B870A31
  955:d=6  hl=2 l=  10 cons: SEQUENCE
  957:d=7  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
  967:d=6  hl=2 l=  38 cons: SEQUENCE
  969:d=7  hl=2 l=  36 cons: SET
  971:d=8  hl=2 l=  34 cons: SEQUENCE
  973:d=9  hl=2 l=   3 prim: OBJECT            :commonName
  978:d=9  hl=2 l=  27 prim: UTF8STRING        :highway-test.example.com
 1007:d=6  hl=2 l=  30 cons: SEQUENCE
 1009:d=7  hl=2 l=  13 prim: UTCTIME           :210413214016Z
 1024:d=7  hl=2 l=  13 prim: UTCTIME           :230413214016Z
 1039:d=6  hl=2 l=  40 cons: SEQUENCE
 1041:d=7  hl=2 l=  38 cons: SET
 1043:d=8  hl=2 l=  36 cons: SEQUENCE
 1045:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 1050:d=9  hl=2 l=  29 prim: UTF8STRING        :highway-test.example.com
 1081:d=6  hl=2 l=  89 cons: SEQUENCE
 1083:d=7  hl=2 l=  19 cons: SEQUENCE
 1085:d=8  hl=2 l=   7 prim: OBJECT            :id-ecPublicKey
 1094:d=8  hl=2 l=   8 prim: OBJECT            :prime256v1
 1104:d=7  hl=2 l=  66 prim: BIT STRING
 1172:d=6  hl=2 l=  16 cons: cont [ 3 ]
 1174:d=7  hl=2 l=  14 cons: SEQUENCE
 1176:d=8  hl=2 l=  12 cons: SEQUENCE
 1178:d=9  hl=2 l=   3 prim: OBJECT            :X509v3 Basic Constraints
 1183:d=9  hl=2 l=   1 prim: BOOLEAN           :255
 1186:d=9  hl=2 l=   2 prim: OCTET STRING      [HEX DUMP]:3000
 1190:d=5  hl=2 l=  10 cons: SEQUENCE
 1192:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 1202:d=5  hl=2 l= 105 prim: BIT STRING
 1309:d=3  hl=4 l= 261 cons: SET
 1313:d=4  hl=4 l= 257 cons: SEQUENCE
 1317:d=5  hl=2 l=   1 prim: INTEGER           :01
 1320:d=5  hl=2 l=  46 cons: SEQUENCE
 1322:d=6  hl=2 l=  38 cons: SEQUENCE
 1324:d=7  hl=2 l=  36 cons: SET
 1326:d=8  hl=2 l=  34 cons: SEQUENCE
 1328:d=9  hl=2 l=   3 prim: OBJECT            :commonName
 1333:d=9  hl=2 l=  27 prim: UTF8STRING        :highway-test.example.com
 1362:d=6  hl=2 l=   4 prim: INTEGER           :0B870A31
 1368:d=5  hl=2 l=  11 cons: SEQUENCE
 1370:d=6  hl=2 l=   9 prim: OBJECT            :sha256
 1381:d=5  hl=2 l= 105 cons: cont [ 0 ]
 1383:d=6  hl=2 l=  24 cons: SEQUENCE
 1385:d=7  hl=2 l=   9 prim: OBJECT            :contentType
 1396:d=7  hl=2 l=  11 cons: SET
 1398:d=8  hl=2 l=   9 prim: OBJECT            :pkcs7-data
 1409:d=6  hl=2 l=  28 cons: SEQUENCE
 1411:d=7  hl=2 l=   9 prim: OBJECT            :signingTime
 1422:d=7  hl=2 l=  15 cons: SET
 1424:d=8  hl=2 l=  13 prim: UTCTIME           :210413214324Z
 1439:d=6  hl=2 l=  47 cons: SEQUENCE
 1441:d=7  hl=2 l=   9 prim: OBJECT            :messageDigest
 1452:d=7  hl=2 l=  34 cons: SET
 1454:d=8  hl=2 l=  32 prim: OCTET STRING      [HEX DUMP]:55148E0E166153
 1488:d=5  hl=2 l=  10 cons: SEQUENCE
 1490:d=6  hl=2 l=   8 prim: OBJECT            :ecdsa-with-SHA256
 1500:d=5  hl=2 l=  72 prim: OCTET STRING      [HEX DUMP]:3046022100E854

Acknowledgements

   We would like to thank the various reviewers for their input, in
   particular William Atwood, Brian Carpenter, Fuyu Eleven, Eliot Lear,
   Sergey Kasatkin, Anoop Kumar, Tom Petch, Markus Stenberg, Peter van
   der Stok, and Thomas Werner.

   Significant reviews were done by Jari Arkko, Christian Huitema, and
   Russ Housley.

   Henk Birkholz contributed the CDDL for the audit-log response.

   This document started its life as a two-page idea from Steinthor
   Bjarnason.

   In addition, significant review comments were provided by many IESG
   members, including Adam Roach, Alexey Melnikov, Alissa Cooper,
   Benjamin Kaduk, Éric Vyncke, Roman Danyliw, and Magnus Westerlund.

Authors' Addresses

   Max Pritikin
   Cisco

   Email: pritikin@cisco.com

   Michael C. Richardson
   Sandelman Software Works

   Email: mcr+ietf@sandelman.ca
   URI:   http://www.sandelman.ca/

   Toerless Eckert
   Futurewei Technologies Inc.  USA
   2330 Central Expy
   Santa Clara, CA 95050
   United States of America

   Email: tte+ietf@cs.fau.de

   Michael H. Behringer

   Email: Michael.H.Behringer@gmail.com

   Kent Watsen
   Watsen Networks

   Email: kent+ietf@watsen.net