SLH-DSA for JOSE and COSE

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Table of Contents

1. Introduction

This document describes JSON Object Signing and Encryption (JOSE) and CBOR Object Signing and Encryption (COSE) 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.¶

This document does not define any new cryptography, only serializations of existing cryptographic systems described in [FIPS-205].¶

This document builds on the Algorithm Key Pair (AKP) type as defined in [I-D.draft-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 requests the registration of the following algorithms in [IANA.jose]:¶

This document requests the registration of the following algorithms in [IANA.cose]:¶

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.draft-ietf-cose-dilithium]. This ensures compatibility across different cryptographic algorithms that use AKP for key representation.¶

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 algorithm that corresponds to the key. Like ML-DSA keys, SLH-DSA keys use the AKP Key Type.¶

The thumbprints for SLH-DSA keys are also computed according to the process described in [I-D.draft-ietf-cose-dilithium]¶

5. Security Considerations

The security considerations of [RFC7515], [RFC7517] and [RFC9053] applies 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.¶

6. IANA Considerations

7. References

Appendix A. Examples

{
  "kty": "AKP",
  "alg": "SLH-DSA-SHA2-128s",
  "pub": "V53SIdVF...uvw2nuCQ",
  "priv": "V53SIdVF...cDKLbsBY"
}

{
  "kty": "AKP",
  "alg": "SLH-DSA-SHA2-128s",
  "pub": "V53SIdVF...uvw2nuCQ"
}

{
  "alg": "SLH-DSA-SHA2-128s"
}

eyJhbGciOiJ...LCJraWQiOiI0MiJ9\
.\
eyJpc3MiOiJ1cm46d...XVpZDo0NTYifQ\
.\
5MSEgQ0dZB4SeLC...AAAAAABIhMUE

{                                   / COSE Key                    /
  1: 7,                             / AKP Key Type                /
  3: -51,                           / SLH-DSA-SHA2-128s Algorithm /
  -1: h'7803c0f9...3f6e2c70',       / AKP Private Key             /
  -2: h'7803c0f9...3bba7abd',       / AKP Public Key              /
}
~~~
{: #SLH-DSA-SHA2-128s-private-cose-key title="Example SLH-DSA-SHA2-128s Private COSE Key"}

~~~~ cbor-diag
{                                   / COSE Key                    /
  1: 7,                             / AKP Key Type                /
  3: -51,                           / SLH-DSA-SHA2-128s Algorithm /
  -2: h'7803c0f9...3bba7abd',       / AKP Public Key              /
}

/ cose-sign1 / 18(
  [
    / protected / <<{
      / algorithm / 1 : -51 / SLH-DSA-SHA2-128s /
    }>>
    / unprotected / {},
    / payload / h'66616b65',
    / signature / h'53e855e8...0f263549'
  ]
)

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.¶

Authors' Addresses