Internet DRAFT - draft-jones-webauthn-secp256k1
draft-jones-webauthn-secp256k1
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
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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
present.
3. ECDSA Signature with secp256k1 Curve
The ECDSA signature algorithm is defined in [DSS]. Implementations
need to check that the key type is "EC" for JOSE or "EC2" (2) for
COSE when creating or verifying a signature.
The ECDSA algorithm specified in this document is:
+--------------+---------------------------+------------------------+
| JOSE Alg | COSE Alg Value | Description |
| Name | | |
+--------------+---------------------------+------------------------+
| ES256K | TBD (requested assignment | ECDSA w/ secp256k1 |
| | -43) | Curve |
+--------------+---------------------------+------------------------+
Table 1: ECDSA Algorithm Values
4. IANA Considerations
4.1. JSON Web Key Elliptic Curve Registration
This section registers the following value in the IANA "JSON Web Key
Elliptic Curve" registry [IANA.JOSE.Curves].
o Curve Name: P-256K
o Curve Description: SECG secp256k1 Curve
o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]]
4.2. JOSE Algorithm Registration
This section registers the following value in the IANA "JSON Web
Signature and Encryption Algorithms" registry [IANA.JOSE.Algorithms].
o Algorithm Name: ES256K
o Algorithm Description: ECDSA w/ secp256k1 Curve
o Algorithm Usage Locations: alg
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o JOSE Implementation Requirements: Optional
o Change Controller: IESG
o Reference: Section 3 of [[ this specification ]]
o Algorithm Analysis Document(s): [SEC2]
4.3. COSE Elliptic Curves Registration
This section registers the following value in the IANA "COSE Elliptic
Curves" registry [IANA.COSE.Curves].
o Name: P-256K
o Value: TBD (requested assignment 8)
o Key Type: EC2
o Description: SECG secp256k1 Curve
o Change Controller: IESG
o Reference: Section 2 of [[ this specification ]]
o Recommended: Yes
4.4. COSE Algorithm Registration
This section registers the following value in the IANA "COSE
Algorithms" registry [IANA.COSE.Algorithms].
o Name: ES256K
o Value: TBD (requested assignment -43)
o Description: ECDSA w/ secp256k1 Curve
o Reference: Section 3 of this document
o Recommended: Yes
5. Security Considerations
Care should be taken that a secp256k1 key not be mistaken for a P-256
key, given that their representations are the same except for the
"crv" value.
The procedures and security considerations described in the [SEC1],
[SEC2], and [DSS] specifications apply to implementations of this
specification.
6. References
6.1. Normative References
[DSS] National Institute of Standards and Technology (NIST),
"Digital Signature Standard (DSS)", FIPS PUB 186-4, July
2013, <http://nvlpubs.nist.gov/nistpubs/FIPS/
NIST.FIPS.186-4.pdf>.
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[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>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/info/rfc7515>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/info/rfc7517>.
[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
RFC 8152, DOI 10.17487/RFC8152, July 2017,
<https://www.rfc-editor.org/info/rfc8152>.
[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>.
[SEC1] Standards for Efficient Cryptography Group, "SEC 1:
Elliptic Curve Cryptography", Version 2.0, May 2009,
<http://www.secg.org/sec1-v2.pdf>.
[SEC2] Standards for Efficient Cryptography Group, "SEC 2:
Recommended Elliptic Curve Domain Parameters",
Version 2.0, January 2010,
<http://www.secg.org/sec2-v2.pdf>.
6.2. Informative References
[IANA.COSE.Algorithms]
IANA, "COSE Algorithms",
<https://www.iana.org/assignments/cose/
cose.xhtml#algorithms>.
[IANA.COSE.Curves]
IANA, "COSE Elliptic Curves",
<https://www.iana.org/assignments/cose/
cose.xhtml#elliptic-curves>.
[IANA.JOSE.Algorithms]
IANA, "JSON Web Signature and Encryption Algorithms",
<https://www.iana.org/assignments/jose/
jose.xhtml#web-signature-encryption-algorithms>.
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[IANA.JOSE.Curves]
IANA, "JSON Web Key Elliptic Curve",
<https://www.iana.org/assignments/jose/
jose.xhtml#web-key-elliptic-curve>.
Acknowledgements
TBD
Document History
[[ to be removed by the RFC Editor before publication as an RFC ]]
-00
o Initial version.
Author's Address
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://self-issued.info/
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