COSE Header parameter for RFC 3161 Time-Stamp Tokens
draft-ietf-cose-tsa-tst-header-parameter-00

COSE Working Group                                           H. Birkholz
Internet-Draft                                            Fraunhofer SIT
Intended status: Standards Track                              T. Fossati
Expires: 13 March 2024                                               arm
                                                             M. Riechert
                                                               Microsoft
                                                       10 September 2023

          COSE Header parameter for RFC 3161 Time-Stamp Tokens
              draft-ietf-cose-tsa-tst-header-parameter-00

Abstract

   RFC 3161 provides a method to time-stamp a message digest to prove
   that it was created before a given time.  This document defines how
   signatures of CBOR Signing And Encrypted (COSE) message structures
   can be time-stamped using RFC 3161 along with the needed header
   parameter to carry the corresponding time-stamp.

Status of This Memo

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   This Internet-Draft will expire on 13 March 2024.

Copyright Notice

   Copyright (c) 2023 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
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   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Notation . . . . . . . . . . . . . . . . . .   2
   2.  RFC 3161 Time-Stamp Tokens COSE Header Parameter  . . . . . .   2
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   This document defines a new COSE [STD96] header parameter that
   carries the TST output of RFC 3161.

1.1.  Requirements Notation

   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.  RFC 3161 Time-Stamp Tokens COSE Header Parameter

   The use of RFC 3161 Time-Stamp Tokens, often in combination with
   X.509 certificates, allows for an existing trust infrastructure to be
   used with COSE.

   The new COSE header parameter for carrying time-stamp tokens is
   defined as:

   *  Name: rfc3161-tst

   *  Label: TBD

   *  Value Type: bstr / [2*bstr]

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   *  Value Registry: none

   *  Description: One or more RFC 3161 time-stamp tokens.

   *  Reference: TBD

   FIXME(tho) The content of the byte string are the bytes of the DER-
   encoded RFC 3161 TimeStampToken structure.  FooFIXME matches the
   content of the equivalent header attribute defined in [RFC3161] for
   Cryptographic Message Syntax (CMS, see [STD70]) envelopes.

   A rfc3161-tst header parameter allows for a single time-stamp token
   or multiple time-stamp tokens to be carried in COSE header maps.  If
   a single time-stamp token is conveyed, it is placed in a CBOR byte
   string.  If multiple time-stamp tokens are conveyed, a CBOR array of
   two or more byte strings is used, with each time-stamp token being in
   its own byte string.

   Time-stamp tokens in this context are similar to a countersignature
   [RFC9338].  Therefore, the header parameter is included in the
   unprotected header of COSE envelopes.

   When sending a request to an RFC 3161 Time Stamping Authority (TSA,
   see [RFC3161]) to obtain a time-stamp token, the message imprint
   (Section 2.4 of [RFC3161]) of the request MUST be the hash of the
   signature field of the COSE envelope to be time-stamped.  The hash
   algorithm does not have to match the algorithm used for signing the
   COSE message.

   RFC 3161 time-stamp tokens use CMS as signature envelope format.
   [STD70] illustrates details of signature verification and [RFC3161]
   provides the details specific to time-stamp token validation.  The
   payload of the signed time-stamp token is a TSTInfo structure as
   defined in [RFC3161] and contains the message imprint that was sent
   to the TSA.  As part of validation of the COSE envelope, the message
   imprint MUST match the hash of the signature field of the time-
   stamped COSE envelope.  The hash algorithm is contained in the
   message imprint structure, together with the hash itself.

   WHY_ALWAYS_ME?(tho) Explicit guidance is illustrated in Appendix B of
   [RFC3161] via an example that shows how time-stamp tokens can be used
   during signature verification of a time-stamped message when using
   X.509 certificates.

3.  Security Considerations

   Similar security considerations as described in RFC 3161 as well as
   the security considerations of RFC 9338 apply.

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4.  IANA Considerations

   TBD

   IANA is requested to register the new COSE Header parameter described
   in section TBD in the "COSE Header Parameters" registry.

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://doi.org/10.17487/RFC2119>.

   [RFC3161]  Adams, C., Cain, P., Pinkas, D., and R. Zuccherato,
              "Internet X.509 Public Key Infrastructure Time-Stamp
              Protocol (TSP)", RFC 3161, DOI 10.17487/RFC3161, August
              2001, <https://doi.org/10.17487/RFC3161>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://doi.org/10.17487/RFC8174>.

   [STD70]    Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,
              <https://doi.org/10.17487/RFC5652>.

   [STD96]    Schaad, J., "CBOR Object Signing and Encryption (COSE):
              Structures and Process", STD 96, RFC 9052,
              DOI 10.17487/RFC9052, August 2022,
              <https://doi.org/10.17487/RFC9052>.

5.2.  Informative References

   [RFC9338]  Schaad, J., "CBOR Object Signing and Encryption (COSE):
              Countersignatures", STD 96, RFC 9338,
              DOI 10.17487/RFC9338, December 2022,
              <https://doi.org/10.17487/RFC9338>.

Authors' Addresses

   Henk Birkholz
   Fraunhofer SIT
   Rheinstrasse 75
   64295 Darmstadt
   Germany

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   Email: henk.birkholz@sit.fraunhofer.de

   Thomas Fossati
   arm
   Email: Thomas.Fossati@arm.com

   Maik Riechert
   Microsoft
   United Kingdom
   Email: Maik.Riechert@microsoft.com

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