CBOR Object Signing and Encryption M. Prorock Internet-Draft mesur.io Intended status: Standards Track O. Steele Expires: 15 April 2026 Tradeverifyd H. Tschofenig H-BRS 12 October 2025 SLH-DSA for JOSE and COSE draft-ietf-cose-sphincs-plus-06 Abstract This document specifies JSON Object Signing and Encryption (JOSE) and CBOR Object Signing and Encryption (COSE) serializations for Stateless Hash-Based Digital Signature Standard (SLH-DSA), a Post- Quantum Cryptography (PQC) digital signature scheme defined in US NIST FIPS 205. 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-sphincs-plus/draft-ietf-cose-sphincs- plus.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ietf-cose-sphincs-plus/. 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-sphincs-plus. 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/. Prorock, et al. Expires 15 April 2026 [Page 1] Internet-Draft SLH-DSA for JOSE and COSE October 2025 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 15 April 2026. Copyright Notice Copyright (c) 2025 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. The SLH-DSA Algorithm Family . . . . . . . . . . . . . . . . 3 4. SLH-DSA Keys . . . . . . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5.1. Validating Public Keys . . . . . . . . . . . . . . . . . 5 5.2. Side-Channel Attacks . . . . . . . . . . . . . . . . . . 5 5.3. Randomness considerations . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6.1. New COSE Algorithms . . . . . . . . . . . . . . . . . . . 5 6.1.1. SLH-DSA-SHA2-128s . . . . . . . . . . . . . . . . . . 6 6.1.2. SLH-DSA-SHAKE-128s . . . . . . . . . . . . . . . . . 6 6.1.3. SLH-DSA-SHA2-128f . . . . . . . . . . . . . . . . . . 6 6.2. New JOSE Algorithms . . . . . . . . . . . . . . . . . . . 7 6.2.1. SLH-DSA-SHA2-128s . . . . . . . . . . . . . . . . . . 7 6.2.2. SLH-DSA-SHAKE-128s . . . . . . . . . . . . . . . . . 7 6.2.3. SLH-DSA-SHA2-128f . . . . . . . . . . . . . . . . . . 7 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 7.1. Normative References . . . . . . . . . . . . . . . . . . 8 7.2. Informative References . . . . . . . . . . . . . . . . . 9 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 9 A.1. JOSE . . . . . . . . . . . . . . . . . . . . . . . . . . 9 A.1.1. Key Pair . . . . . . . . . . . . . . . . . . . . . . 9 A.1.2. JSON Web Signature . . . . . . . . . . . . . . . . . 9 A.2. COSE . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Prorock, et al. Expires 15 April 2026 [Page 2] Internet-Draft SLH-DSA for JOSE and COSE October 2025 A.2.1. Key Pair . . . . . . . . . . . . . . . . . . . . . . 10 A.2.2. COSE_Sign1 Example . . . . . . . . . . . . . . . . . 10 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 10 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction This document specifies JSON Object Signing and Encryption (JOSE) [RFC7515] and CBOR Object Signing and Encryption (COSE) [RFC9052] serializations for the Stateless Hash-Based Digital Signature Standard (SLH-DSA), which was derived from Version 3.1 of SPHINCS+, a Post-Quantum Cryptography (PQC) based digital signature scheme standardized in [FIPS-205]. This document builds on the Algorithm Key Pair (AKP) type, as defined in [I-D.ietf-cose-dilithium]. The AKP type enables flexible representation of keys used across different post-quantum cryptographic algorithms, including SLH-DSA. 2. Terminology 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. The SLH-DSA Algorithm Family The SLH-DSA Signature Scheme is parameterized to support different security levels. This document introduces the registration of the following algorithms in [IANA.jose]: Prorock, et al. Expires 15 April 2026 [Page 3] Internet-Draft SLH-DSA for JOSE and COSE October 2025 +====================+====================+====================+ | Name | alg | Description | +====================+====================+====================+ | SLH-DSA-SHA2-128s | SLH-DSA-SHA2-128s | JSON Web Signature | | | | Algorithm for SLH- | | | | DSA-SHA2-128s | +--------------------+--------------------+--------------------+ | SLH-DSA-SHAKE-128s | SLH-DSA-SHAKE-128s | JSON Web Signature | | | | Algorithm for SLH- | | | | DSA-SHAKE-128s | +--------------------+--------------------+--------------------+ | SLH-DSA-SHA2-128f | SLH-DSA-SHA2-128f | JSON Web Signature | | | | Algorithm for SLH- | | | | DSA-SHA2-128f | +--------------------+--------------------+--------------------+ Table 1: JOSE Algorithms for SLH-DSA This document introduces the registration of the following algorithms in [IANA.cose]: +====================+============+===============================+ | Name | alg | Description | +====================+============+===============================+ | SLH-DSA-SHA2-128s | TBD1 (-51) | CBOR Object Signing Algorithm | | | | for SLH-DSA-SHA2-128s | +--------------------+------------+-------------------------------+ | SLH-DSA-SHAKE-128s | TBD2 (-52) | CBOR Object Signing Algorithm | | | | for SLH-DSA-SHAKE-128s | +--------------------+------------+-------------------------------+ | SLH-DSA-SHA2-128f | TBD3 (-53) | CBOR Object Signing Algorithm | | | | for SLH-DSA-SHA2-128f | +--------------------+------------+-------------------------------+ Table 2: COSE Algorithms for SLH-DSA 4. SLH-DSA Keys Private and public keys are produced to enable the sign and verify operations for each of the SLH-DSA algorithms. The SLH-DSA Algorithm Family uses the Algorithm Key Pair (AKP) key type, as defined in [I-D.ietf-cose-dilithium]. This ensures compatibility across different cryptographic algorithms that use AKP for key representation. Prorock, et al. Expires 15 April 2026 [Page 4] Internet-Draft SLH-DSA for JOSE and COSE October 2025 The specific algorithms for SLH-DSA, such as SLH-DSA-SHA2-128s, SLH- DSA-SHAKE-128s, and SLH-DSA-SHA2-128f, are defined in this document and are used in the alg value of an AKP key representation to specify the corresponding algorithm. Thumbprints for SLH-DSA keys are computed according to the process described in [I-D.ietf-cose-dilithium]. 5. Security Considerations The security considerations of [RFC7515], [RFC7517] and [RFC9053] apply to this specification as well. A detailed security analysis of SLH-DSA is beyond the scope of this specification; see [FIPS-205] for additional details. The following considerations apply to all parameter sets described in this specification. 5.1. Validating Public Keys All algorithms that operate on public keys require validation before use. For sign, verify and proof schemes, the use of KeyValidate is REQUIRED. 5.2. Side-Channel Attacks Implementations of the signing algorithm SHOULD protect the secret key from side-channel attacks. Any implementation of SLH-DSA signing algorithms SHOULD employ at least the following best practices: * Constant-time operation * Consistent instruction sequence and memory access * Uniform sampling without information leakage 5.3. Randomness considerations All nonces MUST originate from a trusted and cryptographically secure source of randomness. 6. IANA Considerations 6.1. New COSE Algorithms IANA is requested to add the following entries to the COSE Algorithms Registry. Prorock, et al. Expires 15 April 2026 [Page 5] Internet-Draft SLH-DSA for JOSE and COSE October 2025 The following registration templates are provided in accordance with the procedures described in [RFC9053] and [RFC9054]. 6.1.1. SLH-DSA-SHA2-128s * Name: SLH-DSA-SHA2-128s * Value: TBD1 (requested assignment -51) * Description: CBOR Object Signing Algorithm for SLH-DSA-SHA2-128s * Capabilities: [kty] * Change Controller: IETF * Reference: RFC XXXX * Recommended: Yes 6.1.2. SLH-DSA-SHAKE-128s * Name: SLH-DSA-SHAKE-128s * Value: TBD2 (requested assignment -52) * Description: CBOR Object Signing Algorithm for SLH-DSA-SHAKE-128s * Capabilities: [kty] * Change Controller: IETF * Reference: RFC XXXX * Recommended: Yes 6.1.3. SLH-DSA-SHA2-128f * Name: SLH-DSA-SHA2-128f * Value: TBD3 (requested assignment -53) * Description: CBOR Object Signing Algorithm for SLH-DSA-SHA2-128f * Capabilities: [kty] * Change Controller: IETF * Reference: RFC XXXX Prorock, et al. Expires 15 April 2026 [Page 6] Internet-Draft SLH-DSA for JOSE and COSE October 2025 * Recommended: Yes 6.2. New JOSE Algorithms IANA is requested to add the following entries to the JSON Web Signature and Encryption Algorithms Registry. The following completed registration templates are provided as described in [RFC7518]. 6.2.1. SLH-DSA-SHA2-128s * Algorithm Name: SLH-DSA-SHA2-128s * Algorithm Description: SLH-DSA-SHA2-128s as described in FIPS 205. * Algorithm Usage Location(s): alg * JOSE Implementation Requirements: Optional * Change Controller: IETF * Specification Document(s): RFC XXXX * Algorithm Analysis Documents(s): [FIPS-205] 6.2.2. SLH-DSA-SHAKE-128s * Algorithm Name: SLH-DSA-SHAKE-128s * Algorithm Description: SLH-DSA-SHAKE-128s as described in FIPS 205. * Algorithm Usage Location(s): alg * JOSE Implementation Requirements: Optional * Change Controller: IETF * Specification Document(s): RFC XXXX * Algorithm Analysis Documents(s): [FIPS-205] 6.2.3. SLH-DSA-SHA2-128f * Algorithm Name: SLH-DSA-SHA2-128f * Algorithm Description: SLH-DSA-SHA2-128f as described in FIPS 205. Prorock, et al. Expires 15 April 2026 [Page 7] Internet-Draft SLH-DSA for JOSE and COSE October 2025 * Algorithm Usage Location(s): alg * JOSE Implementation Requirements: Optional * Change Controller: IETF * Specification Document(s): RFC XXXX * Algorithm Analysis Documents(s): [FIPS-205] 7. References 7.1. Normative References [FIPS-205] "Stateless Hash-Based Digital Signature Standard", n.d., . [I-D.ietf-cose-dilithium] Prorock, M. and O. Steele, "ML-DSA for JOSE and COSE", Work in Progress, Internet-Draft, draft-ietf-cose- dilithium-09, 12 September 2025, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015, . [RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517, DOI 10.17487/RFC7517, May 2015, . [RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518, DOI 10.17487/RFC7518, May 2015, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Prorock, et al. Expires 15 April 2026 [Page 8] Internet-Draft SLH-DSA for JOSE and COSE October 2025 [RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE): Structures and Process", STD 96, RFC 9052, DOI 10.17487/RFC9052, August 2022, . [RFC9053] Schaad, J., "CBOR Object Signing and Encryption (COSE): Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053, August 2022, . [RFC9054] Schaad, J., "CBOR Object Signing and Encryption (COSE): Hash Algorithms", RFC 9054, DOI 10.17487/RFC9054, August 2022, . 7.2. Informative References [IANA.cose] IANA, "CBOR Object Signing and Encryption (COSE)", . [IANA.jose] IANA, "JSON Object Signing and Encryption (JOSE)", . Appendix A. Examples A.1. JOSE A.1.1. Key Pair { "kty": "AKP", "alg": "SLH-DSA-SHA2-128s", "pub": "V53SIdVF...uvw2nuCQ", "priv": "V53SIdVF...cDKLbsBY" } Figure 1: Example SLH-DSA-SHA2-128s Private JSON Web Key { "kty": "AKP", "alg": "SLH-DSA-SHA2-128s", "pub": "V53SIdVF...uvw2nuCQ" } Figure 2: Example SLH-DSA-SHA2-128s Public JSON Web Key A.1.2. JSON Web Signature Prorock, et al. Expires 15 April 2026 [Page 9] Internet-Draft SLH-DSA for JOSE and COSE October 2025 eyJhbGciOiJ...LCJraWQiOiI0MiJ9\ .\ eyJpc3MiOiJ1cm46d...XVpZDo0NTYifQ\ .\ 5MSEgQ0dZB4SeLC...AAAAAABIhMUE Figure 3: Example SLH-DSA-SHA2-128s Compact JSON Web Signature A.2. COSE A.2.1. Key Pair { 1: 7, 3: -51, -1: h'7803c0f9...3f6e2c70', -2: h'7803c0f9...3bba7abd' } Figure 4: Example SLH-DSA-SHA2-128s Private COSE Key { 1: 7, 3: -51, -2: h'7803c0f9...3bba7abd' } Figure 5: Example SLH-DSA-SHA2-128s Public COSE Key A.2.2. COSE_Sign1 Example 18([ <<{1: -51}>>, {}, h'66616b65', h'53e855e8...0f263549' ]) Figure 6: Example SLH-DSA-SHA2-128s COSE Sign1 Acknowledgments We would like to thank Roy Williams, Cedric Fournet, Simo Sorce, Ilari Liusvaara, Neil Madden, Anders Rundgren, David Waite, and Russ Housley for their review feedback. Contributors Prorock, et al. Expires 15 April 2026 [Page 10] Internet-Draft SLH-DSA for JOSE and COSE October 2025 Rafael Misoczki Google Email: rafaelmisoczki@google.com Michael Osborne IBM Email: osb@zurich.ibm.com Christine Cloostermans NXP Email: christine.cloostermans@nxp.com Authors' Addresses Michael Prorock mesur.io Email: mprorock@mesur.io Orie Steele Tradeverifyd Email: orie@or13.io Hannes Tschofenig University of Applied Sciences Bonn-Rhein-Sieg Germany Email: hannes.tschofenig@gmx.net Prorock, et al. Expires 15 April 2026 [Page 11]