COSE                                                           T. Looker
Internet-Draft                                                     Mattr
Intended status: Standards Track                                M. Jones
Expires: 2 September 2022                                      Microsoft
                                                            1 March 2022


              CBOR Web Token (CWT) Claims in COSE Headers
               draft-looker-cose-cwt-claims-in-headers-00

Abstract

   This document describes how to include CBOR Web Token (CWT) claims in
   the header parameters of any COSE structure.  This functionality
   helps to facilitate applications that wish to make use of CBOR Web
   Token (CWT) claims in encrypted COSE structures and/or COSE
   structures featuring detached signatures, while having some of those
   claims be available before decryption and/or without inspecting the
   detached payload.

Discussion Venues

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

   Source for this draft and an issue tracker can be found at
   https://github.com/tplooker/draft-looker-cose-cwt-claims-in-headers.

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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   This Internet-Draft will expire on 2 September 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Representation  . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
   8.  Informative References  . . . . . . . . . . . . . . . . . . .   3
   Appendix A.  Document History . . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   In some applications of COSE, it is useful to have a standard
   representation of CWT claims [RFC8392] available in the header
   parameters.  These include encrypted COSE structures, which may or
   may not be an encrypted CWT and/or those featuring a detached
   signature.

   Section 5.3 of the JWT RFC [RFC7519] defined a similar mechanism for
   expressing selected JWT based claims as JOSE header parameters.  This
   JWT feature was motivated by the desire to have certain claims, such
   as Key ID values, be visible to software processing the JWT, even
   though the JWT is encrypted.  No corresponding feature was
   standardized for CWTs, which was an omission that this specification
   corrects.

   Directly including CWT claim values as COSE header parameter values
   would not work, since there are conflicts between the numeric header
   parameter assignments and the numeric CWT claim assignments.
   Instead, this specification defines a single header parameter
   registered in the IANA "COSE Header Parameters" registry that creates
   a location to store CWT claims in a COSE header parameter.







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2.  Terminology

3.  Representation

   This document defines the following COSE header parameter:

     +========+================+=======+============+===============+
     | Name   | Label          | Value | Value      | Description   |
     |        |                | Type  | Registry   |               |
     +========+================+=======+============+===============+
     | cwt    | TBD (requested | map   | [IANA.CWT] | location for  |
     | claims | assignment 11) |       |            | CWT claims in |
     |        |                |       |            | COSE headers  |
     +--------+----------------+-------+------------+---------------+

                                 Table 1

4.  Privacy Considerations

   Some of the registered CWT claims may contain privacy-sensitive
   information.  Therefore care must be taken when expressing CWT claims
   in COSE headers.

5.  Security Considerations

   In cases where CWT claims are both present in the payload and the
   header, an application receiving such as structure MUST verify that
   their values are identical, unless the application defines other
   specific processing rules for these claims.

6.  IANA Considerations

   IANA is requested to register the new COSE Header parameter in the
   table in Section 3 in the "COSE Header Parameters" registry
   [IANA.COSE].

7.  Normative References

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

   [IANA.CWT] IANA, "CBOR Web Token (CWT) Claims",
              <https://www.iana.org/assignments/cwt/cwt.xhtml>.

8.  Informative References




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   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
              <https://www.rfc-editor.org/info/rfc7519>.

   [RFC8392]  Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
              "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
              May 2018, <https://www.rfc-editor.org/info/rfc8392>.

Appendix A.  Document History

   -00

   *  Initial version

Authors' Addresses

   Tobias Looker
   Mattr
   Email: tobias.looker@mattr.global


   Michael B. Jones
   Microsoft
   Email: mbj@microsoft.com
   URI:   https://self-issued.info/


























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