Network Working Group O. Steele Internet-Draft Transmute Intended status: Standards Track S. Lasker Expires: 23 December 2024 DataTrails 21 June 2024 COSE Hash Envelope draft-steele-cose-hash-envelope-00 Abstract This document defines new COSE header parameters for signaling that a payload is the 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. 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://OR13.github.io/draft-steele-cose-hash-envelope/draft-steele- cose-hash-envelope.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-steele-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/OR13/draft-steele-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- Drafts is at https://datatracker.ietf.org/drafts/current/. Steele & Lasker Expires 23 December 2024 [Page 1] Internet-Draft COSE Hash Envelope June 2024 Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 23 December 2024. 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/ 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 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 3 2. Header Parameters . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Signed Hash Envelopes Example . . . . . . . . . . . . . . 3 2.2. Protected Header . . . . . . . . . . . . . . . . . . . . 4 2.3. Attached Payload . . . . . . . . . . . . . . . . . . . . 5 2.4. Detached Payload . . . . . . . . . . . . . . . . . . . . 5 3. Encrypted Hashes . . . . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 4.1. Choice of Hash Function . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 5.1. COSE Header Algorithm Parameters . . . . . . . . . . . . 6 5.2. Named Information Hash Algorithm Registry . . . . . . . . 6 6. Normative References . . . . . . . . . . . . . . . . . . . . 7 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction COSE defined detached payloads in Section 2 of [RFC9052], using nil as the payload. Steele & Lasker Expires 23 December 2024 [Page 2] Internet-Draft COSE Hash Envelope June 2024 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. 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. 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. Header Parameters To represent a hash of a detached payload, the following headers are defined: TBD 0: will be assigned by [I-D.ietf-cose-typ-header-parameter], represents the content type of the code envelope, including the protected header and payload 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 Hash_Envelope_Protected_Header = { ; Cryptographic algorithm to use ? &(alg: 1) => int, ; Type of the envelope ? &(typ: TBD_0) => 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 Steele & Lasker Expires 23 December 2024 [Page 3] Internet-Draft COSE Hash Envelope June 2024 ; Content type of the preimage 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 ; Identifier for an artifact repository ; For example: ; pkg:container...image@sha256:244f...9c?repo..._url=dev.example ? &(artifact_repository: TBD) => tstr ; Type of Verifiable Data Structure, e.g. RFC9162_SHA256 ; ? &(verifiable-data-structure: -111) => int, ; additional parameters allows. } Verifiable_Data_Proofs = { ? &(inclusion-proofs: -1) => [ bstr .cbor inclusion-proof ] ? &(consistency-proofs: -2) => [ bstr .cbor consistency-proof ] ; ... other proofs are allowed here. } Hash_Envelope_Unprotected_Header = { ; ? &(verifiable-data-proofs: 222) => Verifiable_Data_Proofs ; ... other unprotected header values are still allowed here. } 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 TBD 0 (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. For example: Steele & Lasker Expires 23 December 2024 [Page 4] Internet-Draft COSE Hash Envelope June 2024 { / alg : ES384 / 1: -35, / kid / 4: h'75726e3a...32636573', / typ / TBD 0: application/hashed+cose / payload_hash_alg sha-256 / TBD 1: 1 / payload_preimage_content_type / TBD 2: application/jwk+json / artifact_repository / TBD 3 : \ pkg:container/image@sha256:244f...?repository_url=dev.example } TBD 0 will be assigned by [I-D.ietf-cose-typ-header-parameter], it represents the content type of the code envelope, which includes the protected header and payload. TBD 1 will be assigned by this draft. TBD 2 will be assigned by this draft. TBD 3 will be assigned by this draft. 2.3. Attached Payload The payload MAY be attached. 18( / COSE Sign 1 / [ h'a4013822...3a616263', / Protected / {} / Unprotected / h'317cedc7...c494e772', / Payload / h'15280897...93ef39e5' / Signature / ] ) 2.4. Detached Payload The payload MAY be detached. 18( / COSE Sign 1 / [ h'a4013822...3a616263', / Protected / {} / Unprotected / nil, / Detached payload / h'15280897...93ef39e5' / Signature / ] ) 3. Encrypted Hashes Should we define this? Steele & Lasker Expires 23 December 2024 [Page 5] Internet-Draft COSE Hash Envelope June 2024 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. 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. 5.2. 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 Steele & Lasker Expires 23 December 2024 [Page 6] Internet-Draft COSE Hash Envelope June 2024 * 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 [I-D.ietf-cose-typ-header-parameter] Jones, M. B. and O. Steele, "COSE "typ" (type) Header Parameter", Work in Progress, Internet-Draft, draft-ietf- cose-typ-header-parameter-05, 3 April 2024, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE): Structures and Process", STD 96, RFC 9052, DOI 10.17487/RFC9052, August 2022, . Acknowledgments The following individuals provided input into the final form of the document: Carsten Bormann, Henk Birkholz, Antoine Delignat-Lavaud, Cedric Fournet. Authors' Addresses Orie Steele Transmute Email: orie@transmute.industries Steve Lasker DataTrails Email: steve.lasker@datatrails.ai Steele & Lasker Expires 23 December 2024 [Page 7]