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WebAuthn Working Group                                          M. Jones
Internet-Draft                                                 Microsoft
Intended status: Informational                               May 2, 2018
Expires: November 3, 2018


           COSE Algorithms for Web Authentication (WebAuthn)
                draft-jones-webauthn-cose-algorithms-01

Abstract

   The W3C Web Authentication (WebAuthn) specification uses COSE
   algorithm identifiers.  This specification registers algorithms in
   the IANA "COSE Algorithms" registry that are used by WebAuthn that
   are not already registered.  Also, they are registered in the IANA
   "JSON Web Signature and Encryption Algorithms" registry, when not
   already registered there.

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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 3, 2018.

Copyright Notice

   Copyright (c) 2018 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
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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of




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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Notation and Conventions . . . . . . . . . .   2
   2.  RSASSA-PKCS1-v1_5 Signature Algorithm . . . . . . . . . . . .   2
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  COSE Algorithms Registrations . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
     4.1.  RSA Key Size Security Considerations  . . . . . . . . . .   4
     4.2.  RSASSA-PKCS1-v1_5 with SHA-2 Security Considerations  . .   4
     4.3.  RSASSA-PKCS1-v1_5 with SHA-1 Security Considerations  . .   4
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   5
   Document History  . . . . . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   This specification defines how to use several algorithms with COSE
   [RFC8152] that are used by the W3C Web Authentication (WebAuthn)
   [WebAuthn] specification.  These algorithms are registered in the
   IANA "COSE Algorithms" registry [IANA.COSE.Algorithms] and also in
   the IANA "JSON Web Signature and Encryption Algorithms" registry
   [IANA.JOSE.Algorithms], when not already registered there.

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.
   Implementations need to check that the key type is 'RSA' when
   creating or verifying a signature.




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   The RSASSA-PKCS1-v1_5 algorithms specified in this document are in
   the following table.

   +-------+-------------------------+---------+-----------------------+
   | Name  | Value                   | Hash    | Description           |
   +-------+-------------------------+---------+-----------------------+
   | RS256 | TBD (requested          | SHA-256 | RSASSA-PKCS1-v1_5 w/  |
   |       | assignment -257)        |         | SHA-256               |
   | RS384 | TBD (requested          | SHA-384 | RSASSA-PKCS1-v1_5 w/  |
   |       | assignment -258)        |         | SHA-384               |
   | RS512 | TBD (requested          | SHA-512 | RSASSA-PKCS1-v1_5 w/  |
   |       | assignment -259)        |         | SHA-512               |
   | RS1   | TBD (requested          | SHA-1   | RSASSA-PKCS1-v1_5 w/  |
   |       | assignment -65535)      |         | SHA-1                 |
   +-------+-------------------------+---------+-----------------------+

                Table 1: RSASSA-PKCS1-v1_5 Algorithm Values

3.  IANA Considerations

3.1.  COSE Algorithms Registrations

   This section registers the following values in the IANA "COSE
   Algorithms" registry [IANA.COSE.Algorithms].

   o  Name: RS256
   o  Value: TBD (requested assignment -257)
   o  Description: RSASSA-PKCS1-v1_5 w/ SHA-256
   o  Reference: Section 2 of this document
   o  Recommended: No

   o  Name: RS384
   o  Value: TBD (requested assignment -258)
   o  Description: RSASSA-PKCS1-v1_5 w/ SHA-384
   o  Reference: Section 2 of this document
   o  Recommended: No

   o  Name: RS512
   o  Value: TBD (requested assignment -259)
   o  Description: RSASSA-PKCS1-v1_5 w/ SHA-512
   o  Reference: Section 2 of this document
   o  Recommended: No

   o  Name: RS1
   o  Value: TBD (requested assignment -65535)
   o  Description: RSASSA-PKCS1-v1_5 w/ SHA-1
   o  Reference: Section 2 of this document
   o  Recommended: Deprecated



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4.  Security Considerations

4.1.  RSA Key Size Security Considerations

   The security considerations on key sizes for RSA algorithms from
   Section 6.1 of [RFC8230] also apply to the RSA algorithms in this
   specification.

4.2.  RSASSA-PKCS1-v1_5 with SHA-2 Security Considerations

   The security considerations on the use of RSASSA-PKCS1-v1_5 with
   SHA-2 hash functions from Section 8.3 of [RFC7518] also apply to
   their use in this specification.  For that reason, these algorithms
   are registered as being "Not Recommended".

4.3.  RSASSA-PKCS1-v1_5 with SHA-1 Security Considerations

   The security considerations on the use of the SHA-1 hash function
   from [RFC6194] apply in this specification.  For that reason, the
   "RS1" algorithm is registered as "Deprecated".  It MUST NOT be used
   by COSE implementations.

   A COSE algorithm identifier for this algorithm is nonetheless being
   registered because deployed TPMs continue to use it, and therefore
   WebAuthn implementations need a COSE algorithm identifier for "RS1"
   when TPM attestations using this algorithm are being represented.

5.  References

5.1.  Normative References

   [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>.

   [RFC6194]  Polk, T., Chen, L., Turner, S., and P. Hoffman, "Security
              Considerations for the SHA-0 and SHA-1 Message-Digest
              Algorithms", RFC 6194, DOI 10.17487/RFC6194, March 2011,
              <https://www.rfc-editor.org/info/rfc6194>.

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

   [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>.



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   [RFC7518]  Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
              DOI 10.17487/RFC7518, May 2015,
              <https://www.rfc-editor.org/info/rfc7518>.

   [RFC8017]  Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch,
              "PKCS #1: RSA Cryptography Specifications Version 2.2",
              RFC 8017, DOI 10.17487/RFC8017, November 2016,
              <https://www.rfc-editor.org/info/rfc8017>.

   [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>.

   [RFC8230]  Jones, M., "Using RSA Algorithms with CBOR Object Signing
              and Encryption (COSE) Messages", RFC 8230,
              DOI 10.17487/RFC8230, September 2017,
              <https://www.rfc-editor.org/info/rfc8230>.

5.2.  Informative References

   [IANA.COSE.Algorithms]
              IANA, "COSE Algorithms",
              <https://www.iana.org/assignments/cose/
              cose.xhtml#algorithms>.

   [IANA.JOSE.Algorithms]
              IANA, "JSON Web Signature and Encryption Algorithms",
              <https://www.iana.org/assignments/jose/
              jose.xhtml#web-signature-encryption-algorithms>.

   [WebAuthn]
              Balfanz, D., Czeskis, A., Hodges, J., Jones, J., Jones,
              M., Kumar, A., Liao, A., Lindemann, R., and E. Lundberg,
              "Web Authentication: An API for accessing Public Key
              Credentials",  Candidate Recommendation, World Wide Web
              Consortium (W3C) Recommendation-track, March 2018,
              <https://w3c.github.io/webauthn/>.

Acknowledgements

   Thanks to John Fontana, Jeff Hodges, Tony Nadalin, Jim Schaad, Goeran
   Selander, Wendy Seltzer, Sean Turner, and Samuel Weiler for their
   roles in registering these algorithm identifiers.




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Document History

   [[ to be removed by the RFC Editor before publication as an RFC ]]

   -01

   o  Updated the requested RS1 value from -262 to -65535 to match the
      temporary registration made on 2018-04-19.

   o  Populated the Acknowledgements section.

   -00

   o  Initial version.

Author's Address

   Michael B. Jones
   Microsoft

   Email: mbj@microsoft.com
   URI:   http://self-issued.info/





























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