Using secp256k1 with JOSE and COSE
draft-jones-webauthn-secp256k1-00

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WebAuthn Working Group                                          M. Jones
Internet-Draft                                                 Microsoft
Intended status: Informational                              May 30, 2018
Expires: December 1, 2018

                   Using secp256k1 with JOSE and COSE
                   draft-jones-webauthn-secp256k1-00

Abstract

   This specification defines algorithm encodings and representations
   enabling the Standards for Efficient Cryptography Group (SECG)
   elliptic curve "secp256k1" to be used for JSON Object Signing and
   Encryption (JOSE) and CBOR Object Signing and Encryption (COSE)
   messages.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on December 1, 2018.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Notation and Conventions . . . . . . . . . .   2
   2.  JOSE and COSE secp256k1 Curve Key Representations . . . . . .   2
   3.  ECDSA Signature with secp256k1 Curve  . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  JSON Web Key Elliptic Curve Registration  . . . . . . . .   3
     4.2.  JOSE Algorithm Registration . . . . . . . . . . . . . . .   3
     4.3.  COSE Elliptic Curves Registration . . . . . . . . . . . .   4
     4.4.  COSE Algorithm Registration . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   6
   Document History  . . . . . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   This specification defines algorithm encodings and representations
   enabling the Standards for Efficient Cryptography Group (SECG)
   elliptic curve "secp256k1" [SEC2] to be used for JSON Object Signing
   and Encryption (JOSE) [RFC7515] and CBOR Object Signing and
   Encryption (COSE) [RFC8152] messages.  The elliptic curve and
   associated algorithm are registered in appropriate IANA JOSE and COSE
   registries.

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.  JOSE and COSE secp256k1 Curve Key Representations

   The Standards for Efficient Cryptography Group (SECG) elliptic curve
   "secp256k1" [SEC2] is represented in a JSON Web Key (JWK) [RFC7517]
   using these values:

   o  "kty": "EC"
   o  "crv": "P-256K"

   plus "x" and "y" values to represent the curve point for the key.
   Other optional values such as "alg" MAY also be present.

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   It is represented in a COSE_Key [RFC8152] using these values:

   o  "kty" (1): "EC2" (2)
   o  "crv" (-1): "P-256K" (TBD - requested assignment 8)

   plus "x" (-2) and "y" (-3) values to represent the curve point for
   the key.  Other optional values such as "alg" (3) MAY also be
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