CBOR Object Signing and Encryption (COSE) and JSON Object Signing and Encryption (JOSE) Registrations for Web Authentication (WebAuthn) Algorithms
RFC 8812

Document Type RFC - Proposed Standard (August 2020; No errata)
Last updated 2020-08-14
Replaces draft-jones-cose-additional-algorithms
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Internet Engineering Task Force (IETF)                          M. Jones
Request for Comments: 8812                                     Microsoft
Category: Standards Track                                    August 2020
ISSN: 2070-1721

 CBOR Object Signing and Encryption (COSE) and JSON Object Signing and
   Encryption (JOSE) Registrations for Web Authentication (WebAuthn)
                               Algorithms

Abstract

   The W3C Web Authentication (WebAuthn) specification and the FIDO
   Alliance FIDO2 Client to Authenticator Protocol (CTAP) specification
   use CBOR Object Signing and Encryption (COSE) algorithm identifiers.
   This specification registers the following algorithms (which are used
   by WebAuthn and CTAP implementations) in the IANA "COSE Algorithms"
   registry: RSASSA-PKCS1-v1_5 using SHA-256, SHA-384, SHA-512, and SHA-
   1; and Elliptic Curve Digital Signature Algorithm (ECDSA) using the
   secp256k1 curve and SHA-256.  It registers the secp256k1 elliptic
   curve in the IANA "COSE Elliptic Curves" registry.  Also, for use
   with JSON Object Signing and Encryption (JOSE), it registers the
   algorithm ECDSA using the secp256k1 curve and SHA-256 in the IANA
   "JSON Web Signature and Encryption Algorithms" registry and the
   secp256k1 elliptic curve in the IANA "JSON Web Key Elliptic Curve"
   registry.

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/rfc8812.

Copyright Notice

   Copyright (c) 2020 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
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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   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.  Requirements Notation and Conventions
   2.  RSASSA-PKCS1-v1_5 Signature Algorithm
   3.  Using secp256k1 with JOSE and COSE
     3.1.  JOSE and COSE secp256k1 Curve Key Representations
     3.2.  ECDSA Signature with secp256k1 Curve
     3.3.  Other Uses of the secp256k1 Elliptic Curve
   4.  IANA Considerations
     4.1.  COSE Algorithms Registrations
     4.2.  COSE Elliptic Curves Registrations
     4.3.  JOSE Algorithms Registrations
     4.4.  JSON Web Key Elliptic Curves Registrations
   5.  Security Considerations
     5.1.  RSA Key Size Security Considerations
     5.2.  RSASSA-PKCS1-v1_5 with SHA-2 Security Considerations
     5.3.  RSASSA-PKCS1-v1_5 with SHA-1 Security Considerations
     5.4.  secp256k1 Security Considerations
   6.  References
     6.1.  Normative References
     6.2.  Informative References
   Acknowledgements
   Author's Address

1.  Introduction

   This specification defines how to use several algorithms with CBOR
   Object Signing and Encryption (COSE) [RFC8152] that are used by
   implementations of the W3C Web Authentication (WebAuthn) [WebAuthn]
   and FIDO Alliance FIDO2 Client to Authenticator Protocol (CTAP)
   [CTAP] specifications.  This specification registers these algorithms
   in the IANA "COSE Algorithms" registry [IANA.COSE.Algorithms] and
   registers an elliptic curve in the IANA "COSE Elliptic Curves"
   registry [IANA.COSE.Curves].  This specification also registers a
   corresponding algorithm for use with JSON Object Signing and
   Encryption (JOSE) [RFC7515] in the IANA "JSON Web Signature and
   Encryption Algorithms" registry [IANA.JOSE.Algorithms] and registers
   an elliptic curve in the IANA "JSON Web Key Elliptic Curve" registry
   [IANA.JOSE.Curves].

1.1.  Requirements Notation and Conventions

   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.

2.  RSASSA-PKCS1-v1_5 Signature Algorithm

   The RSASSA-PKCS1-v1_5 signature algorithm is defined in [RFC8017].
   The RSASSA-PKCS1-v1_5 signature algorithm is parameterized with a
   hash function (h).

   A key of size 2048 bits or larger MUST be used with these algorithms.
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