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Coordinating the Use of Application Profiles for Ephemeral Diffie-Hellman Over COSE (EDHOC)
draft-tiloca-lake-app-profiles-01

Document Type Active Internet-Draft (individual)
Authors Marco Tiloca , Rikard Höglund
Last updated 2024-03-04
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draft-tiloca-lake-app-profiles-01
LAKE Working Group                                             M. Tiloca
Internet-Draft                                                R. Höglund
Intended status: Standards Track                                 RISE AB
Expires: 5 September 2024                                   4 March 2024

   Coordinating the Use of Application Profiles for Ephemeral Diffie-
                       Hellman Over COSE (EDHOC)
                   draft-tiloca-lake-app-profiles-01

Abstract

   The lightweight authenticated key exchange protocol Ephemeral Diffie-
   Hellman Over COSE (EDHOC) requires certain parameters to be agreed
   out-of-band, in order to ensure its successful completion.  To this
   end, application profiles specify the intended use of EDHOC to allow
   for the relevant processing and verifications to be made.  This
   document defines a number of means to coordinate the use and
   discovery of EDHOC application profiles.  Also, it defines a
   canonical, CBOR-based representation that can be used to describe,
   distribute, and store EDHOC application profiles.  Finally, it
   defines a well-known EDHOC application profile.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Discussion of this document takes place on the Lightweight
   Authenticated Key Exchange Working Group mailing list
   (lake@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/lake/.

   Source for this draft and an issue tracker can be found at
   https://gitlab.com/crimson84/draft-tiloca-lake-app-profiles.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on 5 September 2024.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Web Linking . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  EDHOC_Information Parameters  . . . . . . . . . . . . . . . .   5
     3.1.  Use in the EDHOC and OSCORE Profile of the ACE
           Framework . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Representation of an EDHOC Application Profile  . . . . . . .   6
   5.  Well-known EDHOC Application Profile  . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  Media Type Registrations  . . . . . . . . . . . . . . . .  10
     7.2.  CoAP Content-Formats Registry . . . . . . . . . . . . . .  11
     7.3.  EDHOC Application Profiles Registry . . . . . . . . . . .  11
     7.4.  Target Attributes Registry  . . . . . . . . . . . . . . .  12
     7.5.  EDHOC Information Registry  . . . . . . . . . . . . . . .  12
     7.6.  Expert Review Instructions  . . . . . . . . . . . . . . .  13
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .  13
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   Ephemeral Diffie-Hellman Over COSE (EDHOC) [I-D.ietf-lake-edhoc] is a
   lightweight authenticated key exchange protocol, especially intended
   for use in constrained scenarios.

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   In order to successfully run EDHOC, the two peers acting as Initiator
   and Responder have to agree on certain parameters.  Some of those are
   in-band and communicated through the protocol execution, during which
   a few of them may even be negotiated.  However, other parameters have
   to be known out-of-band, before running the EDHOC protocol.

   As discussed in Section 3.9 of [I-D.ietf-lake-edhoc], applications
   can use EDHOC application profiles, which specify the intended usage
   of EDHOC to allow for the relevant processing and verifications to be
   made.  In particular, an EDHOC application profile may include both
   in-band and out-of-band parameters.

   This document defines a number of means to coordinate the use and
   discovery of EDHOC application profiles, that is:

   *  The new IANA registry "EDHOC Application Profiles" defined in
      Section 7.3, where to register integer identifiers of EDHOC
      application profiles.

   *  The new target attribute "ed-prof" defined in Section 2, which can
      be used in a web link [RFC8288] to an EDHOC resource.  This can be
      used, for instance, in a link-format document [RFC6690] describing
      EDHOC resources at a server, when EDHOC is transferred over CoAP
      [RFC7252], see Appendix A.2 of [I-D.ietf-lake-edhoc] as well as
      [I-D.ietf-core-oscore-edhoc].

   *  The new parameter "app_prof" for the EDHOC_Information object
      specified in [I-D.ietf-ace-edhoc-oscore-profile].  The parameter
      is defined in Section 3, and can be used, for example, in the
      EDHOC and OSCORE profile of the ACE framework
      [I-D.ietf-ace-edhoc-oscore-profile] to indicate the EDHOC
      application profiles supported by a Resource Server.

   Furthermore, this document defines a canonical, CBOR-based
   representation that can be used to describe, distribute, and store
   EDHOC application profiles (see Section 4), as well as a well-known
   EDHOC application profile (see Section 5).

1.1.  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.

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   The reader is expected to be familiar with terms and concepts defined
   in EDHOC [I-D.ietf-lake-edhoc], and with the use of EDHOC with CoAP
   [RFC7252] and OSCORE [RFC8613] defined in
   [I-D.ietf-core-oscore-edhoc].

   Concise Binary Object Representation (CBOR) [RFC8949] and Concise
   Data Definition Language (CDDL) [RFC8610] are used in this document.
   CDDL predefined type names, especially bstr for CBOR byte strings and
   tstr for CBOR text strings, are used extensively in this document.

2.  Web Linking

   Section 6 of [I-D.ietf-core-oscore-edhoc] defines a number of target
   attributes that can be used in a web link [RFC8288] with resource
   type "core.edhoc" (see Section 10.10 of [I-D.ietf-lake-edhoc]).  This
   is the case, e.g., when using a link-format document [RFC6690]
   describing EDHOC resources at a server, when EDHOC is transferred
   over CoAP [RFC7252] as defined in Appendix A.2 of
   [I-D.ietf-lake-edhoc].  This allows a client to obtain relevant
   pieces of information from the EDHOC application profile(s) to be
   used with a certain EDHOC resource.

   In the same spirit, this section defines the following additional
   parameter, which can be optionally specified as a target attribute
   with the same name in the link to the respective EDHOC resource, or
   among the filter criteria in a discovery request from a client.

   *  'ed-prof', specifying an EDHOC application profile supported by
      the server.  This parameter MUST specify a single value, which is
      taken from the 'Profile ID' column of the "EDHOC Application
      Profiles" registry defined in Section 7.3 of this document.  This
      parameter MAY occur multiple times, with each occurrence
      specifying an EDHOC application profile.

   When specifying the parameter 'ed-prof' in a link to an EDHOC
   resource, the target attribute rt="core.edhoc" MUST be included.

   If a link to an EDHOC resource includes occurrences of the target
   attribute 'ed-prof', the link MUST NOT include other target
   attributes that provide information pertaining to an EDHOC
   application profile (see, e.g., Section 6 of
   [I-D.ietf-core-oscore-edhoc]), which, if present, MUST be ignored by
   the recipient.

   The example in Figure 1 shows how a CoAP client discovers two EDHOC
   resources at a CoAP server, obtaining information elements from the
   respective application profile.  The Link Format notation from
   Section 5 of [RFC6690] is used.

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   The example assumes the existence of an EDHOC application profile
   identified by the integer Profile ID 500, which is supported by the
   EDHOC resource at /edhoc-alt.

      REQ: GET /.well-known/core

      RES: 2.05 Content
          </sensors/temp>;osc,
          </sensors/light>;if=sensor,
          </.well-known/edhoc>;rt=core.edhoc;ed-csuite=0;ed-csuite=2;
              ed-method=0;ed-cred-t=1;ed-cred-t=3;ed-idcred-t=4;
              ed-i;ed-r;ed-comb-req,
          </edhoc-alt>;rt=core.edhoc;ed-prof=500

                          Figure 1: The Web Link.

3.  EDHOC_Information Parameters

   Section 3.4 of [I-D.ietf-ace-edhoc-oscore-profile] defines the
   EDHOC_Information object, as including information that guides two
   peers towards executing the EDHOC protocol, and defines an initial
   set of its parameters.

   This document defines the new parameter "app_prof" of the
   EDHOC_Information object, as summarized in Figure 2 and described
   further below.

       +----------+-------+-------+-------------+-----------------+
       | Name     | CBOR  | CBOR  | Registry    | Description     |
       |          | label | type  |             |                 |
       +----------+-------+-------+-------------+-----------------+
       | app_prof | 14    | int / | EDHOC       | Set of          |
       |          |       | array | Application | supported EDHOC |
       |          |       |       | Profiles    | Application     |
       |          |       |       | Registry    | Profiles        |
       +----------+-------+-------+-------------+-----------------+

              Figure 2: EDHOC_Information Parameter "app_prof"

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   *  app_prof: This parameter specifies a set of supported EDHOC
      application profiles, identified by their Profile ID.  If the set
      is composed of a single EDHOC application profile, its Profile ID
      is encoded as an integer.  Otherwise, the set is encoded as an
      array of integers, where each array element encodes one Profile
      ID.  In JSON, the "app_prof" value is an integer or an array of
      integers.  In CBOR, "app_prof" is an integer or an array of
      integers, and has label 14.  The integer values are taken from the
      'Profile ID' column of the "EDHOC Application Profiles" registry
      defined in Section 7.3 of this document.

3.1.  Use in the EDHOC and OSCORE Profile of the ACE Framework

   Section 3.2 of [I-D.ietf-ace-edhoc-oscore-profile] defines how the
   EDHOC_Information object can be used within the workflow of the EDHOC
   and OSCORE transport profile of the ACE framework for authentication
   and authorization in constrained environments (ACE) [RFC9200].

   In particular, the AS-to-C Access Token Response can include the
   parameter "edhoc_info", with value an EDHOC_Information object.  This
   allows the ACE Authorization Server (AS) to provide the ACE Client
   (C) with information about how to run the EDHOC protocol with the ACE
   Resource Server (RS) for which the Access Token is issued.

   In such a case, the EDHOC_Information object above can include the
   parameter "app_prof" defined in this document.  This parameter
   indicates a set of EDHOC application profiles associated with the
   EDHOC resource to use at the RS, which is either implied or specified
   by the parameter "uri_path" within the same EDHOC_Information object.

   If the EDHOC_Information object specified as value of "edhoc_info"
   includes the "app_prof" parameter, the object MUST NOT include other
   parameters that provide information pertaining to an EDHOC
   application profile.  Such parameters MUST be ignored by C, if
   present in an EDHOC_Information object that also includes the
   "app_prof" parameter.

   At the time of writing this document, such parameters are: "methods",
   "cipher_suites", "message_4", "comb_req", "osc_ms_len",
   "osc_salt_len", "osc_version", "cred_types", "id_cred_types", "eads",
   "initiator", and "responder".  These are all defined in Section 3.4
   of [I-D.ietf-ace-edhoc-oscore-profile].

4.  Representation of an EDHOC Application Profile

   This section defines the EDHOC_Application_Profile object, which can
   be used as a canonical representation of EDHOC application profiles
   for their description, distribution, and storage.

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   An EDHOC_Application_Profile object is encoded as a CBOR map
   [RFC8949].  Each element of the CBOR map is an element of the CBOR-
   encoded EDHOC_Information object defined in Section 3.3 of
   [I-D.ietf-ace-edhoc-oscore-profile], and thus uses the corresponding
   CBOR abbreviations from the 'CBOR label' column of the "EDHOC
   Information" registry defined in [I-D.ietf-ace-edhoc-oscore-profile].

   The CBOR map encoding the EDHOC application profile MUST include the
   element "app_prof" defined in this document.  Its value is the unique
   identifier of the EDHOC application profile in question, taken from
   the 'Profile ID' column of the "EDHOC Application Profiles" registry
   defined in this document, and encoded as a CBOR integer.

   The following elements defined for the EDHOC_Information object MUST
   also be present: "methods" and "cred_types".

   The following elements defined for the EDHOC_Information object MUST
   NOT be present: "session_id", "uri_path", "initiator", and
   "responder".

   The CBOR map MAY include other elements defined for the
   EDHOC_Information object.  Consistently with Sections 8 and A.1 of
   [I-D.ietf-lake-edhoc] and with Section 5.4 of [RFC8613]:

   *  If the element "cipher_suites" is not present in the CBOR map,
      this indicates that the EDHOC application profile uses the EDHOC
      cipher suites 2 and 3.

   *  If the element "id_cred_types" is not present in the CBOR map,
      this indicates that the EDHOC application profile uses "kid" as
      type of authentication credential identifiers for EDHOC.

   *  If the element "osc_ms_len" is not present in the CBOR map, this
      indicates that, when using EDHOC to key OSCORE [RFC8613], the size
      of the OSCORE Master Secret in bytes is equal to the size of the
      key length for the application AEAD Algorithm of the selected
      cipher suite for the EDHOC session.

   *  If the element "osc_salt_len" is not present in the CBOR map, this
      indicates that, when using EDHOC to key OSCORE, the size of the
      OSCORE Master Salt in bytes is 8.

   *  If the element "osc_version" is not present in the CBOR map, this
      indicates that, when using EDHOC to key OSCORE, the OSCORE Version
      Number has value 1.

   *  The absence of any other elements in the CBOR map MUST NOT result
      in assuming any value.

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   If an element is present in the CBOR map and the information that it
   specifies is intrinsically a set of one or more co-existing
   alternatives, then all the specified alternatives apply for the EDHOC
   application profile in question.

   For example, the element "cipher_suites" with value the CBOR array
   [0, 2] means that, in order to adhere to the EDHOC application
   profile in question, an EDHOC peer has to implement both the EDHOC
   cipher suites 0 and 2, because either of them can be used by another
   EDHOC peer also adhering to the same EDHOC application profile.

   The CDDL grammar describing the EDHOC_Application_Profile object is:

   EDHOC_Application_Profile = {
         1 => int / array,    ; methods
         9 => int / array,    ; cred_types
        14 => int,            ; app_prof
      * int / tstr => any
   }

   [ NOTE:

   Based on Sections 3.9 and F of [I-D.ietf-lake-edhoc], further
   parameters can be defined for the EDHOC_Information object specified
   in Section 3.4 of [I-D.ietf-ace-edhoc-oscore-profile], and then used
   for the EDHOC_Application_Profile object defined in this document.
   For example:

   *  The way(s) to express the identity of endpoints within
      authentication credentials, e.g., EUI-64.

   *  Limitations in the size of EDHOC messages (see Section 3.4 of
      [I-D.ietf-lake-edhoc]).

   *  The transport(s) to use for EDHOC.  How to indicate that?  It is
      actually about multiple pieces of information, often transport-
      dependent.

      -  For example, if CoAP is indicated, it should be said over what
         CoAP is in turn transported, if any of the EDHOC-related CoAP
         Content-Format has to be indicated, etc.  See, for instance,
         point 1 in Sections 3.9 and F of [I-D.ietf-lake-edhoc].

         This might require another registry about "transport suites" to
         be used with EDHOC, each of which registered with a unique
         identifier, specifying the transport protocol together with
         additional (transport-dependent) pieces of information.

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      -  At the same time, Section 3.9 of [I-D.ietf-lake-edhoc] says:

         "Note that it is not necessary for the endpoints to specify a
         single transport for the EDHOC messages.  For example, a mix of
         CoAP and HTTP may be used along the path, and this may still
         allow correlation between messages."

         In order to take this into account, an application profile can
         specify two sets of supported transports, i.e., with a
         parameter "tp_i" pertaining to an Initiator that uses this
         profile and a parameter "tp_r" pertaining to a Responder that
         uses this profile.  The two sets can independently specify the
         expected support for multiple transports, each together with
         related transport-dependent information.

         In order to handle the case where both "tp_i" and "tp_r" are
         equal, a single parameter "tp" can be used instead.  In that
         case, an Initiator and a Responder using this profile are
         expected to use any of the transports from the set specified by
         the parameter "tp".

   ]

5.  Well-known EDHOC Application Profile

   TBD

   [ NOTE:

   This well-known EDHOC application profile is _not_ intended to be a
   "default" profile to use, in case no other indication is provided to
   the EDHOC peers.

   With particular reference to using EDHOC with CoAP, it must _not_ be
   silently assumed that, unless otherwise indicated, the EDHOC resource
   at /.well-known/edhoc is used according to such a well-known profile.

   If this well-known EDHOC application profile was treated as a
   "default" profile, it might be suggesting what is generally mandatory
   to implement, which is instead limited to what is already defined by
   the compliance requirements in Section 8 of [I-D.ietf-lake-edhoc]
   (i.e., simply support for "kid" as type of credential identifier, as
   well as for cipher suites 2 and 3).

   That is, this well-known EDHOC application profile is _not_ intended
   to practically replace the compliance requirements from Section 8 of
   [I-D.ietf-lake-edhoc], which defines what is a de-facto, unnamed
   default EDHOC application profile.

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   Instead, this well-known EDHOC application profile should reflect
   what is the most common and expected way to use EDHOC.

   ]

6.  Security Considerations

   TBD

7.  IANA Considerations

   This document has the following actions for IANA.

   Note to RFC Editor: Please replace all occurrences of "[RFC-XXXX]"
   with the RFC number of this specification and delete this paragraph.

7.1.  Media Type Registrations

   IANA is asked to register the media type "application/edhoc-app-
   profile+cbor-seq".  This registration follows the procedures
   specified in [RFC6838].

   Type name: application

   Subtype name: edhoc-app-profile+cbor-seq

   Required parameters: N/A

   Optional parameters: N/A

   Encoding considerations: Must be encoded as a CBOR sequence [RFC8742]
   of CBOR maps.  Each element of each CBOR map is also defined as an
   element of the CBOR-encoded EDHOC_Information object from Section 3.3
   of [I-D.ietf-ace-edhoc-oscore-profile].

   Security considerations: See Section 6 of [RFC-XXXX].

   Interoperability considerations: N/A

   Published specification: [RFC-XXXX]

   Applications that use this media type: Applications that need to
   describe, distribute, and store a representation of an EDHOC
   application profile (see Section 3.9 of [I-D.ietf-lake-edhoc]).

   Fragment identifier considerations: N/A

   Additional information: N/A

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   Person & email address to contact for further information: LAKE WG
   mailing list (lake@ietf.org) or IETF Applications and Real-Time Area
   (art@ietf.org)

   Intended usage: COMMON

   Restrictions on usage: None

   Author/Change controller: IETF

   Provisional registration: No

7.2.  CoAP Content-Formats Registry

   IANA is asked to add the following entry to the "CoAP Content-
   Formats" registry within the "Constrained RESTful Environments (CoRE)
   Parameters" registry group.

   Content Type: application/edhoc-app-profile+cbor-seq

   Content Coding: -

   ID: TBD

   Reference: [RFC-XXXX]

7.3.  EDHOC Application Profiles Registry

   IANA is requested to create a new "EDHOC Application Profiles"
   registry within the "Ephemeral Diffie-Hellman Over COSE (EDHOC)"
   registry group defined in [I-D.ietf-lake-edhoc].

   The registry uses the "Expert Review" registration procedure
   [RFC8126].  Expert Review guidelines are provided in Section 7.6.
   Values in this registry are covered by different registration
   policies as indicated.  It should be noted that, in addition to the
   expert review, some portions of the registry require a specification,
   potentially a Standards Track RFC, to be supplied as well.

   The columns of this registry are:

   *  Profile ID: This field contains the value used to identify the
      EDHOC application profile.  These values MUST be unique.  The
      value can be an unsigned integer or a negative integer.  Different
      ranges of values use different registration policies [RFC8126]:

      -  Integer values from -24 to 23 are designated as "Standards
         Action With Expert Review".

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      -  Integer values from -65536 to -25 and from 24 to 65535 are
         designated as "Specification Required".

      -  Integer values smaller than -65536 and greater than 65535 are
         marked as "Private Use".

   *  Name: This field contains the name of the EDHOC application
      profile.

   *  Description: This field contains a short description of the EDHOC
      application profile.

   *  Reference: This field contains a pointer to the public
      specification for the EDHOC application profile.

7.4.  Target Attributes Registry

   IANA is asked to register the following entry in the "Target
   Attributes" registry within the "Constrained RESTful Environments
   (CoRE) Parameters", as per [I-D.ietf-core-target-attr].

   *  Attribute Name: ed-prof

   *  Brief Description: A supported EDHOC application profile

   *  Change Controller: IETF

   *  Reference: [RFC-XXXX]

7.5.  EDHOC Information Registry

   IANA is asked to register the following entry in the "EDHOC
   Information" registry defined in [I-D.ietf-ace-edhoc-oscore-profile].

   *  Name: app_prof

   *  CBOR Value: 14

   *  CBOR Type: int / array

   *  Registry: EDHOC Application Profiles Registry

   *  Description: Set of supported EDHOC Application Profiles

   *  Specification: [RFC-XXXX], [I-D.ietf-lake-edhoc]

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7.6.  Expert Review Instructions

   The IANA registry established in this document is defined as "Expert
   Review".  This section gives some general guidelines for what the
   experts should be looking for; but they are being designated as
   experts for a reason, so they should be given substantial latitude.

   Expert reviewers should take into consideration the following points:

   *  Clarity and correctness of registrations.  Experts are expected to
      check the clarity of purpose and use of the requested entries.
      Experts need to make sure that registered identifiers indicate an
      EDHOC application profile that is clearly defined in the
      corresponding specification.  Identifiers of EDHOC application
      profiles that do not meet these objective of clarity and
      completeness must not be registered.

   *  Point squatting should be discouraged.  Reviewers are encouraged
      to get sufficient information for registration requests to ensure
      that the usage is not going to duplicate one that is already
      registered and that the point is likely to be used in deployments.
      The zones tagged as "Private Use" are intended for testing
      purposes and closed environments.  Code points in other ranges
      should not be assigned for testing.

   *  Specifications are required for the "Standards Action With Expert
      Review" range of point assignment.  Specifications should exist
      for "Specification Required" ranges, but early assignment before a
      specification is available is considered to be permissible.  When
      specifications are not provided, the description provided needs to
      have sufficient information to identify what the point is being
      used for.

   *  Experts should take into account the expected usage of fields when
      approving point assignment.  The fact that there is a range for
      Standards Track documents does not mean that a Standards Track
      document cannot have points assigned outside of that range.  The
      length of the encoded value should be weighed against how many
      code points of that length are left, the size of device it will be
      used on, and the number of code points left that encode to that
      size.

8.  Normative References

   [COSE.Header.Parameters]
              IANA, "COSE Header Parameters",
              <https://www.iana.org/assignments/cose/cose.xhtml#header-
              parameters>.

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   [I-D.ietf-ace-edhoc-oscore-profile]
              Selander, G., Mattsson, J. P., Tiloca, M., and R. Höglund,
              "Ephemeral Diffie-Hellman Over COSE (EDHOC) and Object
              Security for Constrained Environments (OSCORE) Profile for
              Authentication and Authorization for Constrained
              Environments (ACE)", Work in Progress, Internet-Draft,
              draft-ietf-ace-edhoc-oscore-profile-03, 23 October 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-ace-
              edhoc-oscore-profile-03>.

   [I-D.ietf-core-oscore-edhoc]
              Palombini, F., Tiloca, M., Höglund, R., Hristozov, S., and
              G. Selander, "Using Ephemeral Diffie-Hellman Over COSE
              (EDHOC) with the Constrained Application Protocol (CoAP)
              and Object Security for Constrained RESTful Environments
              (OSCORE)", Work in Progress, Internet-Draft, draft-ietf-
              core-oscore-edhoc-10, 29 November 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-core-
              oscore-edhoc-10>.

   [I-D.ietf-core-target-attr]
              Bormann, C., "CoRE Target Attributes Registry", Work in
              Progress, Internet-Draft, draft-ietf-core-target-attr-06,
              11 October 2023, <https://datatracker.ietf.org/doc/html/
              draft-ietf-core-target-attr-06>.

   [I-D.ietf-lake-edhoc]
              Selander, G., Mattsson, J. P., and F. Palombini,
              "Ephemeral Diffie-Hellman Over COSE (EDHOC)", Work in
              Progress, Internet-Draft, draft-ietf-lake-edhoc-23, 22
              January 2024, <https://datatracker.ietf.org/doc/html/
              draft-ietf-lake-edhoc-23>.

   [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/rfc/rfc2119>.

   [RFC6690]  Shelby, Z., "Constrained RESTful Environments (CoRE) Link
              Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
              <https://www.rfc-editor.org/rfc/rfc6690>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/rfc/rfc6838>.

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   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014,
              <https://www.rfc-editor.org/rfc/rfc7252>.

   [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/rfc/rfc8126>.

   [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/rfc/rfc8174>.

   [RFC8288]  Nottingham, M., "Web Linking", RFC 8288,
              DOI 10.17487/RFC8288, October 2017,
              <https://www.rfc-editor.org/rfc/rfc8288>.

   [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/rfc/rfc8610>.

   [RFC8613]  Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
              "Object Security for Constrained RESTful Environments
              (OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019,
              <https://www.rfc-editor.org/rfc/rfc8613>.

   [RFC8742]  Bormann, C., "Concise Binary Object Representation (CBOR)
              Sequences", RFC 8742, DOI 10.17487/RFC8742, February 2020,
              <https://www.rfc-editor.org/rfc/rfc8742>.

   [RFC8949]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", STD 94, RFC 8949,
              DOI 10.17487/RFC8949, December 2020,
              <https://www.rfc-editor.org/rfc/rfc8949>.

   [RFC9200]  Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and
              H. Tschofenig, "Authentication and Authorization for
              Constrained Environments Using the OAuth 2.0 Framework
              (ACE-OAuth)", RFC 9200, DOI 10.17487/RFC9200, August 2022,
              <https://www.rfc-editor.org/rfc/rfc9200>.

Acknowledgments

   The authors sincerely thank Christian Amsüss, Göran Selander, and
   Brian Sipos for their feedback and comments.

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Authors' Addresses

   Marco Tiloca
   RISE AB
   Isafjordsgatan 22
   SE-16440 Stockholm Kista
   Sweden
   Email: marco.tiloca@ri.se

   Rikard Höglund
   RISE AB
   Isafjordsgatan 22
   SE-16440 Stockholm Kista
   Sweden
   Email: rikard.hoglund@ri.se

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