SLH-DSA for JOSE and COSE
draft-ietf-cose-sphincs-plus-06
| Document | Type | Active Internet-Draft (cose WG) | |
|---|---|---|---|
| Authors | Michael Prorock , Orie Steele , Hannes Tschofenig | ||
| Last updated | 2025-10-12 | ||
| Replaces | draft-ietf-cose-post-quantum-signatures | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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draft-ietf-cose-sphincs-plus-06
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/.
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Internet-Drafts are draft documents valid for a maximum of six months
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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
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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
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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]:
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+====================+====================+====================+
| 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.
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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.
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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
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* 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.
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* 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.,
<https://doi.org/10.6028/NIST.FIPS.205>.
[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,
<https://datatracker.ietf.org/doc/html/draft-ietf-cose-
dilithium-09>.
[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>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/rfc/rfc7515>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/rfc/rfc7517>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<https://www.rfc-editor.org/rfc/rfc7518>.
[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>.
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[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>.
[RFC9053] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053,
August 2022, <https://www.rfc-editor.org/rfc/rfc9053>.
[RFC9054] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Hash Algorithms", RFC 9054, DOI 10.17487/RFC9054, August
2022, <https://www.rfc-editor.org/rfc/rfc9054>.
7.2. Informative References
[IANA.cose]
IANA, "CBOR Object Signing and Encryption (COSE)",
<https://www.iana.org/assignments/cose>.
[IANA.jose]
IANA, "JSON Object Signing and Encryption (JOSE)",
<https://www.iana.org/assignments/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
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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
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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
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