COSE Profiles

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Table of Contents

1. Introduction

COSE [STD96] is not an end-to-end system with guaranteed interoperability. It is designed to serve a range of use cases and therefore it has a lot of options. In general, two COSE implementations that want to interoperate require an agreement on which subset of COSE features they will use.¶

This document provides a set of rules for specifying such agreements as "COSE profiles" and registers a new COSE header parameter for in-band signalling of profile information.¶

2. Conventions and Definitions

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.¶

3. Profiling Rules

A COSE profile:¶

• MUST be specified in a document¶

• MUST NOT change the syntax or semantics of any already defined header attribute¶

  • but does allow restricting their values¶

• MAY define new header attributes¶

  • if so, it MUST provide their definition in the same document¶
• MUST use CDDL [RFC8610] to fully specify the syntax rules for the profile¶

• MUST use the cose-profile header attribute (see Section 4) in the protected header¶

  • The value of cose-profile MUST be globally unique. Possible choices include:¶

    • IANA registry (Section 8.2)¶
    • using an OID [RFC9090], URI [STD66] or CRI [I-D.ietf-core-href]¶
    • using a UUID [RFC4122]¶
  • The chosen value SHOULD be appropriate for the intended usage scope (e.g., a short value when used in constrained node environments)¶
• MAY define its own CBOR tag that can be used together with, or in lieu of, the underlying COSE CBOR tag (Table 1, Section 2 of [STD96])¶
• SHOULD define its complementary media-type and content-format¶

4. COSE profile header parameter

COSE-profile = registered-profile / oid-profile / uri-profile
             / cri-profile / uuid-profile
registered-profile = int
oid-profile = oid ; tagged
uri-profile = ~uri ; unwrapped -- any tstr is a uri
cri-profile = cri
uuid-profile = uuid ; naked bstr is a UUID

uuid = bstr .size 16

; imported from RFC 9090
oid = #6.111(bstr)
; import from CRI spec when ready
cri = [*any]

5. Profile Registration Template

Note: This is just an initial sketch.¶

Tracked at: https://github.com/ietf-rats-wg/draft-ietf-rats-corim/issues/10¶

• What is the profile identifier?¶
• Requires certain header keys?¶
• Constrains any header keys?¶
• Constrains any header values?¶
• Defines new header keys?¶
• Defines its own CBOR Tag?¶
• Defines its own Media Type?¶
• What payload(s) allows?¶

6. CoSWID COSE Profile Definition

Note: This is just an initial sketch.¶

Tracked at: https://github.com/ietf-rats-wg/draft-ietf-rats-corim/issues/10¶

This section defines the COSE profile for CoSWID [I-D.ietf-sacm-coswid].¶

This definition is semantically and syntactically equivalent with what is described in Section 7 of [I-D.ietf-sacm-coswid], with the exception of the explicit CoSWID COSE profile indicator that is added to the protected header.¶

protected-signed-coswid-header = {
  &(alg: 1) => int
  &(content-type: 3) => "application/swid+cbor"
  &(cose-profile-CPA: 13) => &(CoSWID-COSE-profile-CPA: 0)
  * cose-label => cose-values
}

cose-label = int / text
cose-values = any

7. Security Considerations

TODO Security¶

8. IANA Considerations

Appendix A. GlueCOSE Test Cases

The community effort [GlueCOSE] provides test vectors for the COSE specification.¶

The CDDL definition for the test vector format used for COSE profiles will be provided in a future version of this document.¶

Tracked at: https://github.com/ietf-rats-wg/draft-ietf-rats-corim/issues/4¶

Acknowledgments

Laurence Lundblade who - unknowingly :-) - provided the introduction.¶

Authors' Addresses