Internet DRAFT - draft-birkholz-cose-tsa-tst-header-parameter
draft-birkholz-cose-tsa-tst-header-parameter
TBD H. Birkholz
Internet-Draft Fraunhofer SIT
Intended status: Standards Track M. Riechert
Expires: 14 September 2023 Microsoft
13 March 2023
COSE Header parameter for RFC 3161 Time-Stamp Tokens
draft-birkholz-cose-tsa-tst-header-parameter-01
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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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 14 September 2023.
Copyright Notice
Copyright (c) 2023 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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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. Privacy Considerations . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
Useful new COSE [STD96] header member that is 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: RFC 3161 time-stamp tokens
* Label: TBD
* Value Type: bstr / [2*bstr]
* Value Registry: none
* Description: One or more RFC 3161 time-stamp tokens.
* Reference: TBD
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The content of the byte string are the bytes of the DER-encoded RFC
3161 TimeStampToken structure. This matches the content of the
equivalent header attribute defined in [RFC3161] for Cryptographic
Message Syntax (CMS, see [STD70]) envelopes.
This header parameter allows for a single time-stamp token or
multiple time-stamp tokens to be carried in the message. 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 byte strings
is used, with each time-stamp token being in its own byte string.
Given that time-stamp tokens in this context are similar to a
countersignature [RFC9338], the header parameter can be included in
the unprotected header of a COSE envelope.
When sending a request to an RFC 3161 Time Stamping Authority (TSA,
see [RFC3161]) to obtain a time-stamp token, then the so-called
message imprint (Section 2.4 of [RFC3161]) of the request MUST be the
hash of the bytes within the byte string of the signature field of
the COSE structure 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]
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, the message imprint MUST be matched to the
hash of the bytes within the byte string of the signature field of
the time-stamped COSE structure. The hash algorithm is contained in
the message imprint structure, together with the hash itself.
Appendix B of RFC 3161 provides an example of how time-stamp tokens
can be used during signature verification of a time-stamped message
when using X.509 certificates.
3. Privacy Considerations
TBD
4. Security Considerations
TBD
Similar security considerations as described in RFC 3161 apply.
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5. IANA Considerations
TBD
IANA is requested to register the new COSE Header parameter described
in section TBD in the "COSE Header Parameters" registry.
6. References
6.1. 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>.
6.2. 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
Maik Riechert
Microsoft
United Kingdom
Email: Maik.Riechert@microsoft.com
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