COSE Hash Envelope
draft-ietf-cose-hash-envelope-00
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| Authors | Orie Steele , Steve Lasker , Henk Birkholz | ||
| Last updated | 2024-08-16 (Latest revision 2024-08-15) | ||
| Replaces | draft-steele-cose-hash-envelope | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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draft-ietf-cose-hash-envelope-00
Network Working Group O. Steele
Internet-Draft Transmute
Intended status: Standards Track S. Lasker
Expires: 16 February 2025 DataTrails
H. Birkholz
Fraunhofer SIT
15 August 2024
COSE Hash Envelope
draft-ietf-cose-hash-envelope-00
Abstract
This document defines new COSE header parameters for signaling a
payload as an output of a hash function. This mechanism enables
faster validation as access to the original payload is not required
for signature validation. Additionally, hints of the detached
payload's content format and availability are defined providing
references to optional discovery mechanisms that can help to find
original payload content.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at https://cose-
wg.github.io/draft-ietf-cose-hash-envelope/draft-ietf-cose-hash-
envelope.html. Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ietf-cose-hash-envelope/.
Discussion of this document takes place on the CBOR Object Signing
and Encryption Working Group mailing list (mailto:cose@ietf.org),
which is archived at https://mailarchive.ietf.org/arch/browse/cose/.
Subscribe at https://www.ietf.org/mailman/listinfo/cose/.
Source for this draft and an issue tracker can be found at
https://github.com/cose-wg/draft-ietf-cose-hash-envelope.
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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
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This Internet-Draft will expire on 16 February 2025.
Copyright Notice
Copyright (c) 2024 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
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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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. Attached Payload . . . . . . . . . . . . . . . . . . . . 3
1.2. Detached Payload . . . . . . . . . . . . . . . . . . . . 3
1.3. Hashed Payload . . . . . . . . . . . . . . . . . . . . . 3
2. Header Parameters . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Signed Hash Envelopes Example . . . . . . . . . . . . . . 4
2.2. Protected Header . . . . . . . . . . . . . . . . . . . . 5
3. Encrypted Hashes . . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
4.1. Choice of Hash Function . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5.1. Requirements Notation . . . . . . . . . . . . . . . . . . 6
5.2. COSE Header Algorithm Parameters . . . . . . . . . . . . 6
5.3. Named Information Hash Algorithm Registry . . . . . . . . 7
6. Normative References . . . . . . . . . . . . . . . . . . . . 7
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
COSE defined detached payloads in Section 2 of [RFC9052], using nil
as the payload. In order to verify a signature over a detached
payload, the verifier must have access to the payload content.
Storing a hash of the content allows for small signature envelopes,
that are easy to transport and verify independently.
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Additional hints in the protected header ensure cryptographic agility
for the hashing & signing algorithms, and discoverability for the
original content which could be prohibitively large to move over a
network.
1.1. Attached Payload
COSE_sign1 envelope with an attached payload, providing for signature
validation.
18( / COSE Sign 1 /
[
h'a4013822...3a616263', / Protected /
{} / Unprotected /
h'317cedc7...c494e772', / Payload /
h'15280897...93ef39e5' / Signature /
]
)
1.2. Detached Payload
COSE_sign1 envelope with a detached payload (nil), which is compact
but the payload must be distributed out of band to validate the
signature
18( / COSE Sign 1 /
[
h'a4013822...3a616263', / Protected /
{} / Unprotected /
nil, / Detached Payload /
h'15280897...93ef39e5' / Signature /
]
)
1.3. Hashed Payload
A hashed payload functions equivalently to an attached payload, with
the benefits of being compact in size and providing the ability to
validate the signature.
18( / COSE Sign 1 /
[
h'a4013822...3a616263', / Protected /
{} / Unprotected /
h'935b5a91...e18a588a', / Payload /
h'15280897...93ef39e5' / Signature /
]
)
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2. Header Parameters
To represent a hash of a payload, the following headers are defined:
TBD_1: the hash algorithm used to generate the hash of the payload
TBD_2: the content type of the payload the hash represents
TBD_3: an identifier enabling a verifier to retrieve the full
payload preimage.
2.1. Signed Hash Envelopes Example
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Hash_Envelope_Protected_Header = {
; Cryptographic algorithm to use
? &(alg: 1) => int,
; Type of the envelope
? &(typ: 16) => int / tstr
; Hash algorithm used to produce the payload from content
; -16 for SHA-256,
; See https://www.iana.org/assignments/cose/cose.xhtml
&(payload_hash_alg: TBD_1) => int
; Content type of the preimage
; (content to be hashed) of the payload
; 50 for application/json,
; See https://datatracker.ietf.org/doc/html/rfc7252#section-12.3
&(payload_preimage_content_type: TBD_2) => int
; Location the content of the hashed payload is stored
; For example:
; storage.example/244f...9c19
? &(payload_location: TBD_3) => tstr
* int => any
}
Hash_Envelope_Unprotected_Header = {
* int => any
}
Hash_Envelope_as_COSE_Sign1 = [
protected : bstr .cbor Hash_Envelope_Protected_Header,
unprotected : Hash_Envelope_Unprotected_Header,
payload: bstr / nil,
signature : bstr
]
Hash_Envelope = #6.18(Hash_Envelope_as_COSE_Sign1)
2.2. Protected Header
16 (typ), TBD_1 (payload hash alg) and TBD_2 (content type of the
preimage of the payload) MUST be present in the protected header and
MUST NOT be present in the unprotected header. TBD_3
(payload_location) MAY be added to the protected header and MUST NOT
be presented in the unprotected header.
For example:
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{
/ alg : ES384 / 1: -35,
/ kid / 4: h'75726e3a...32636573',
/ typ / 16: application/hashed+cose
/ payload_hash_alg sha-256 / TBD_1: 1
/ payload_preimage_content_type / TBD_2: application/jwk+json
/ payload_location / TBD_3 : storage.example/244f...9c19
}
3. Encrypted Hashes
Should we define this?
4. Security Considerations
TODO Security
4.1. Choice of Hash Function
It is RECOMMENDED to align the strength of the chosen hash function
to the strength of the chosen signature algorithm. For example, when
signing with ECDSA using P-256 and SHA-256, use SHA-256 to hash the
payload.
5. IANA Considerations
5.1. 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.
5.2. COSE Header Algorithm Parameters
* Name: payload hash algorithm
* Label: TBD_1
* Value type: int
* Value registry: https://www.iana.org/assignments/named-
information/named-information.xhtml
* Description: Hash algorithm used to produce the payload.
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5.3. Named Information Hash Algorithm Registry
* Name: SHAKE256
* Label: TBD_2
* Value type: int
* Value registry: https://www.iana.org/assignments/named-
information/named-information.xhtml
* Description: SHAKE256 a described in
https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.202.pdf
* Name: ASCON128
* Label: TBD_3
* Value type: int
* Value registry: https://www.iana.org/assignments/named-
information/named-information.xhtml
* Description: ASCON128 a described in
https://csrc.nist.gov/CSRC/media/Projects/lightweight-
cryptography/documents/round-2/spec-doc-rnd2/ascon-spec-round2.pdf
6. 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/rfc/rfc2119>.
[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/rfc/rfc8174>.
[RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC9052, August 2022,
<https://www.rfc-editor.org/rfc/rfc9052>.
Acknowledgments
The following individuals provided input into the final form of the
document: Carsten Bormann, Henk Birkholz, Antoine Delignat-Lavaud,
Cedric Fournet.
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Authors' Addresses
Orie Steele
Transmute
Email: orie@transmute.industries
Steve Lasker
DataTrails
Email: steve.lasker@datatrails.ai
Henk Birkholz
Fraunhofer SIT
Rheinstrasse 75
64295 Darmstadt
Germany
Email: henk.birkholz@ietf.contact
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