Use of the ML-DSA Signature Algorithm in the Cryptographic Message Syntax (CMS)
draft-ietf-lamps-cms-ml-dsa-00

Limited Additional Mechanisms for PKIX and SMIME               B. Salter
Internet-Draft                                                  A. Raine
Intended status: Standards Track       UK National Cyber Security Centre
Expires: 8 May 2025                                         D. Van Geest
                                                     CryptoNext Security
                                                         4 November 2024

   Use of the ML-DSA Signature Algorithm in the Cryptographic Message
                              Syntax (CMS)
                     draft-ietf-lamps-cms-ml-dsa-00

Abstract

   The Module-Lattice-Based Digital Signature Algorithm (ML-DSA), as
   defined in FIPS 204, is a post-quantum digital signature scheme that
   aims to be secure against an adversary in posession of a
   Cryptographically Relevant Quantum Computer (CRQC).  This document
   specifies the conventions for using the ML-DSA signature algorithm
   with the Cryptographic Message Syntax (CMS).  In addition, the
   algorithm identifier and public key syntax are provided.

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://lamps-
   wg.github.io/cms-ml-dsa/draft-ietf-lamps-cms-ml-dsa.html.  Status
   information for this document may be found at
   https://datatracker.ietf.org/doc/draft-ietf-lamps-cms-ml-dsa/.

   Discussion of this document takes place on the Limited Additional
   Mechanisms for PKIX and SMIME Working Group mailing list
   (mailto:spasm@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/spasm/.  Subscribe at
   https://www.ietf.org/mailman/listinfo/spasm/.

   Source for this draft and an issue tracker can be found at
   https://github.com/lamps-wg/cms-ml-dsa.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Conventions and Definitions . . . . . . . . . . . . . . .   3
   2.  ML-DSA Algorithm Identifiers  . . . . . . . . . . . . . . . .   4
   3.  ML-DSA Key Encoding . . . . . . . . . . . . . . . . . . . . .   5
   4.  Signed-data Conventions . . . . . . . . . . . . . . . . . . .   6
     4.1.  Pure mode vs pre-hash mode  . . . . . . . . . . . . . . .   6
     4.2.  Signature generation and verification . . . . . . . . . .   7
     4.3.  SignerInfo content  . . . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Appendix A.  ASN.1 Module . . . . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

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1.  Introduction

   The Module-Lattice-Based Digital Signature Algorithm (ML-DSA) is a
   digital signature algorithm standardised by NIST as part of their
   post-quantum cryptography standardization process.  It is intended to
   be secure against both "traditional" cryptographic attacks, as well
   as attacks utilising a quantum computer.  It offers smaller
   signatures and significantly faster runtimes than SLH-DSA [FIPS203],
   an alternative post-quantum signature algorithm also standardised by
   NIST.

   Prior to standardisation, the algorithm was known as Dilithium.  ML-
   DSA and Dilithium are not compatible.

   ML-DSA offers parameter sets that meet three security levels: ML-DSA-
   44, ML-DSA-65, and ML-DSA-87.  ML-DSA-44 is intended to meet NIST's
   level 2 security category, ML-DSA-65 is intended to meet level 3, and
   ML-DSA-87 is intended to meet level 5.  Each category requires that
   algorithms be as resistant to attack as a particular cryptographic
   algorithm.  Attacks on algorithms in the level 2 category are
   intended to be at least as hard as performing a collision search on
   SHA256.  Attacks on algorithms in the level 3 category are intended
   to be at least as hard as performing an exhaustive key search on
   AES192.  Attacks on algorithms in the level 5 category are intended
   to be at least as hard as performing an exhaustive key search on
   AES256.

   EDNOTE: Appendix B of draft-ietf-lamps-dilithium-certificates
   describes this well, if it's easier just to refer to that.

   For each of the ML-DSA parameter sets, an algorithm identifier OID
   has been specified.

   [FIPS204] also specifies a pre-hashed variant of ML-DSA, called
   HashML-DSA.  HashML-DSA is not used in CMS.

1.1.  Conventions and Definitions

   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.

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2.  ML-DSA Algorithm Identifiers

   Many ASN.1 data structure types use the AlgorithmIdentifier type to
   identify cryptographic algorithms.  In CMS, AlgorithmIdentifiers are
   used to identify ML-DSA signatures in the signed-data content type.
   They may also appear in X.509 certificates used to verify those
   signatures.  [I-D.ietf-lamps-dilithium-certificates] describes the
   use of ML-DSA in X.509 certificates.  The AlgorithmIdentifier type,
   which is included herein for convenience, is defined as follows:

   AlgorithmIdentifier{ALGORITHM-TYPE, ALGORITHM-TYPE:AlgorithmSet} ::=
           SEQUENCE {
               algorithm   ALGORITHM-TYPE.&id({AlgorithmSet}),
               parameters  ALGORITHM-TYPE.
                      &Params({AlgorithmSet}{@algorithm}) OPTIONAL
           }

   The above syntax is from [RFC5911] and is compatible with the 2021
   ASN.1 syntax [X680].  See [RFC5280] for the 1988 ASN.1 syntax.

   The fields in the AlgorithmIdentifier type have the following
   meanings:

   algorithm:  The algorithm field contains an OID that identifies the
      cryptographic algorithm in use.  The OIDs for ML-DSA are described
      below.

   parameters:  The parameters field contains parameter information for
      the algorithm identified by the OID in the algorithm field.  Each
      ML-DSA parameter set is identified by its own algorithm OID, so
      there is no relevant information to include in this field.  As
      such, parameters MUST be omitted when encoding an ML-DSA
      AlgorithmIdentifier.

   The object identifiers for ML-DSA are defined in the NIST Computer
   Security Objects Register [CSOR], and are reproduced here for
   convenience.

   sigAlgs OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16)
       us(840) organization(1) gov(101) csor(3) nistAlgorithms(4) 3 }

   id-ml-dsa-44 OBJECT IDENTIFIER ::= { sigAlgs 17 }

   id-ml-dsa-65 OBJECT IDENTIFIER ::= { sigAlgs 18 }

   id-ml-dsa-87 OBJECT IDENTIFIER ::= { sigAlgs 19 }

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3.  ML-DSA Key Encoding

   Section 4 of [I-D.ietf-lamps-dilithium-certificates] describes the
   format of ML-DSA public keys when encoded as a part of the
   SubjectPublicKeyInfo type.  The signed-data content type as described
   in [RFC5652] does not encode public keys directly, but CMS content
   types defined by other documents do.  For example, [RFC5272]
   describes Certificate Management over CMS, and its PKIData content
   utilises the SubjectPublicKeyInfo type to encode public keys for
   certificate requests.  When the SubjectPublicKeyInfo type is used in
   CMS, ML-DSA public keys MUST be encoded as described in
   [I-D.ietf-lamps-dilithium-certificates]

   [RFC5958] describes the Asymmetric Key Package CMS content type, and
   the OneAsymmetricKey type for encoding asymmetric keypairs.  When an
   ML-DSA private key or keypair is encoded as a OneAsymmetricKey, it
   follows the description in Section 6 of
   [I-D.ietf-lamps-dilithium-certificates].

   The ASN.1 descriptions of ML-DSA keys are repeated below for
   convenience.

   EDNOTE: This section should reflect the content of draft-ietf-lamps-
   dilithium-certificates.  The ASN.1 public key definitions in that
   document are not yet fully expanded, so the below is a best guess
   based on the equivalent SLH-DSA keys.  Alternatively, draft-ietf-
   lamps-dilithium-certificates could reflect this document, as is the
   case for the SLH-DSA X.509/CMS drafts.

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   pk-ml-dsa-44 PUBLIC-KEY ::= {
     IDENTIFIER id-ml-dsa-44
     -- KEY no ASN.1 wrapping --
     CERT-KEY-USAGE
       { digitalSignature, nonRepudiation, keyCertSign, cRLSign }
     -- PRIVATE-KEY no ASN.1 wrapping -- }

   pk-ml-dsa-65 PUBLIC-KEY ::= {
     IDENTIFIER id-ml-dsa-65
     -- KEY no ASN.1 wrapping --
     CERT-KEY-USAGE
       { digitalSignature, nonRepudiation, keyCertSign, cRLSign }
     -- PRIVATE-KEY no ASN.1 wrapping -- }

   pk-ml-dsa-87 PUBLIC-KEY ::= {
     IDENTIFIER id-ml-dsa-87
     -- KEY no ASN.1 wrapping --
     CERT-KEY-USAGE
       { digitalSignature, nonRepudiation, keyCertSign, cRLSign }
     -- PRIVATE-KEY no ASN.1 wrapping -- }

   ML-DSA-PublicKey ::= OCTET STRING
   ML-DSA-PrivateKey ::= OCTET STRING

4.  Signed-data Conventions

4.1.  Pure mode vs pre-hash mode

   [RFC5652] specifies that digital signatures for CMS are produced
   using a digest of the message to be signed, and the signer's private
   key.  At the time of publication of that RFC, all signature
   algorithms supported in CMS required a message digest to be
   calculated externally to that algorithm, which would then be supplied
   to the algorithm implementation when calculating and verifying
   signatures.  Since then, EdDSA [RFC8032], SLH-DSA [FIPS203] have also
   been standardised, and these algorithms support both a "pure" and
   "pre-hash" mode.  In the pre-hash mode, a message digest (the "pre-
   hash") is calculated separately and supplied to the signature
   algorithm as described above.  In the pure mode, the message to be
   signed or verified is instead supplied directly to the signature
   algorithm.  ML-DSA also supports a pre-hash and pure mode, though we
   follow the convention set by EdDSA in CMS [RFC8419] and SLH-DSA in
   CMS [I-D.ietf-lamps-cms-sphincs-plus] in that only the pure mode of
   ML-DSA is used in CMS.  That is, the pre-hash mode of ML-DSA MUST NOT
   be used in CMS.

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4.2.  Signature generation and verification

   [RFC5652] describes the two methods that are used to calculate and
   verify signatures in CMS.  One method is used when signed attributes
   are present in the signedAttrs field of the relevant SignerInfo, and
   another is used when signed attributes are absent.  Each method
   produces a different "message digest" to be supplied to the signature
   algorithm in question, but because the pure mode of ML-DSA is used,
   the "message digest" is in fact the entire message.  Use of signed
   attributes is preferred, but the conventions for signed-data without
   signed attributes is also described below for completeness.

   EDNOTE: Would it make sense to make a stronger statement here?  For
   instance, that CMS implements MAY reject signatures if they don't
   contain signed attributes, or that generation/verification of signed-
   data without signed attributes SHOULD NOT be supported?  Some of the
   discussion around the use of context strings for new signature
   algorithms has highlighted the dangers here, as has Falko's paper
   here: https://eprint.iacr.org/2023/1801

   When signed attributes are absent, ML-DSA (pure mode) signatures are
   computed over the content of the signed-data.  As described in
   Section 5.4 of [RFC5652], the "content" of a signed-data is the value
   of the encapContentInfo eContent OCTET STRING.  The tag and length
   octets are not included.

   When signed attributes are included, ML-DSA (pure mode) signatures
   are computed over a DER encoding of the SignerInfo's signedAttrs
   field.  As described in Section 5.4 of [RFC5652], this encoding does
   include the tag and length octets, but an EXPLICIT SET OF tag is used
   rather than the IMPLICIT [0] tag that appears in the final message.
   The signedAttrs field MUST at minimum include a content-type
   attribute and a message-digest attribute.  The message-digest
   attribute contains a hash of the content of the signed-data, where
   the content is as described for the absent signed attributes case
   above.  Recalculation of the hash value by the recipient is an
   important step in signature verification.  Choice of digest algorithm
   is up to the signer; algorithms for each parameter set are
   recommended below.

   Section 4 of [I-D.ietf-lamps-cms-sphincs-plus] describes how, when
   the content of a signed-data is large, performance may be improved by
   including signed attributes.  This is as true for ML-DSA as it is for
   SLH-DSA, although ML-DSA signature generation and verification is
   significantly faster than SLH-DSA.

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   ML-DSA has a context string input that can be used to ensure that
   different signatures are generated for different application
   contexts.  When using ML-DSA as described in this document, the
   context string is not used.

   EDNOTE: It's been suggested that the context string could be used to
   separate content-only/signed attributes signatures.  SLH-DSA and ML-
   DSA should stay in alignment here.  If not specified here, are there
   other ways the context string could be used, e.g. with a different
   algorithm identifier or a signed attribute?  If so, we could add a
   note to signpost that this is could appear in a future standard.

4.3.  SignerInfo content

   When using ML-DSA, the fields of a SignerInfo are used as follows:

   digestAlgorithm:  Per Section 5.3 of [RFC5652], the digestAlgorithm
      field identifies the message digest algorithm used by the signer,
      and any associated parameters.  To ensure collision resistance,
      the identified message digest algorithm SHOULD produce a hash
      value of a size that is at least twice the collision strength of
      the internal commitment hash used by ML-DSA.
      The SHAKE hash functions defined in [FIPS202] are used internally
      by ML-DSA, and hence the combinations in Table 1 are RECOMMENDED
      for use with ML-DSA.  [RFC8702] describes how SHAKE128 and
      SHAKE256 are used in CMS.  The id-shake128 and id-shake256 digest
      algorithm identifiers are used and the parameters field MUST be
      omitted.

            +=====================+==========================+
            | Signature algorithm | Message digest algorithm |
            +=====================+==========================+
            | ML-DSA-44           | SHAKE128                 |
            +---------------------+--------------------------+
            | ML-DSA-65           | SHAKE256                 |
            +---------------------+--------------------------+
            | ML-DSA-87           | SHAKE256                 |
            +---------------------+--------------------------+

              Table 1: Recommended message digest algorithms
                     for ML-DSA signature algorithms

   signatureAlgorithm:  When signing a signed-data using ML-DSA, the
      signatureAlgorithm field MUST contain one of the ML-DSA signature
      algorithm OIDs, and the parameters field MUST be absent.  The
      algorithm OID MUST be one of the following OIDs described in
      Section 2:

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            +=====================+==========================+
            | Signature algorithm | Algorithm Identifier OID |
            +=====================+==========================+
            | ML-DSA-44           | id-ml-dsa-44             |
            +---------------------+--------------------------+
            | ML-DSA-65           | id-ml-dsa-65             |
            +---------------------+--------------------------+
            | ML-DSA-87           | id-ml-dsa-87             |
            +---------------------+--------------------------+

               Table 2: Signature algorithm identifier OIDs
                                for ML-DSA

   signature:  The signature field contains the signature value
      resulting from the use of the ML-DSA signature algorithm
      identified by the signatureAlgorithm field.  The ML-DSA (pure
      mode) signature generation operation is specified in Section 5.2
      of [FIPS204], and the signature verification operation is
      specified in Section 5.3 of [FIPS204].  Note that Section 5.6 of
      [RFC5652] places further requirements on the successful
      verification of a signature.

5.  Security Considerations

   The relevant security considerations from [RFC5652] apply to this
   document as well.

   The security considerations for
   [I-D.ietf-lamps-dilithium-certificates] are equally applicable to
   this document.

   Security of the ML-DSA private key is critical.  Compromise of the
   private key will enable an adversary to forge arbitrary signatures.

   By default ML-DSA signature generation uses randomness from two
   sources: fresh random data generated during signature generation, and
   precomputed random data included in the signer's private key.  This
   is referred to as the "hedged" variant of ML-DSA.  Inclusion of both
   sources of random can help mitigate against faulty random number
   generators and side-channel attacks.  [FIPS204] also permits creating
   deterministic signatures using just the precomputed random data in
   the signer's private key.  The signer SHOULD NOT use the
   deterministic variant of ML-DSA on platforms where side-channel
   attacks are a concern.

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6.  IANA Considerations

   IANA is requested to assign an object identifier for id-mod-ml-dsa-
   2024, for the ASN.1 module identifier found in Appendix A.  This
   should be allocated in the "SMI Security for PKIX Module Identifier"
   registry (1.3.6.1.5.5.7.0).

7.  Acknowledgments

   TODO acknowledgements.

8.  References

8.1.  Normative References

   [CSOR]     NIST, "Computer Security Objects Register", 20 August
              2024, <https://csrc.nist.gov/projects/computer-security-
              objects-register/algorithm-registration>.

   [FIPS204]  NIST, "Module-Lattice-Based Digital Signature Standard",
              13 August 2024,
              <https://csrc.nist.gov/pubs/fips/204/final>.

   [I-D.ietf-lamps-dilithium-certificates]
              Massimo, J., Kampanakis, P., Turner, S., and B.
              Westerbaan, "Internet X.509 Public Key Infrastructure:
              Algorithm Identifiers for ML-DSA", Work in Progress,
              Internet-Draft, draft-ietf-lamps-dilithium-certificates-
              05, 4 November 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-lamps-
              dilithium-certificates-05>.

   [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>.

   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
              RFC 5652, DOI 10.17487/RFC5652, September 2009,
              <https://www.rfc-editor.org/rfc/rfc5652>.

   [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>.

8.2.  Informative References

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   [FIPS202]  "SHA-3 standard :: permutation-based hash and extendable-
              output functions", National Institute of Standards and
              Technology (U.S.), DOI 10.6028/nist.fips.202, 2015,
              <https://doi.org/10.6028/nist.fips.202>.

   [FIPS203]  "Module-Lattice-Based Key-Encapsulation Mechanism
              Standard", National Institute of Standards and Technology,
              DOI 10.6028/nist.fips.203, August 2024,
              <https://doi.org/10.6028/nist.fips.203>.

   [I-D.ietf-lamps-cms-sphincs-plus]
              Housley, R., Fluhrer, S., Kampanakis, P., and B.
              Westerbaan, "Use of the SLH-DSA Signature Algorithm in the
              Cryptographic Message Syntax (CMS)", Work in Progress,
              Internet-Draft, draft-ietf-lamps-cms-sphincs-plus-12, 4
              November 2024, <https://datatracker.ietf.org/doc/html/
              draft-ietf-lamps-cms-sphincs-plus-12>.

   [RFC5272]  Schaad, J. and M. Myers, "Certificate Management over CMS
              (CMC)", RFC 5272, DOI 10.17487/RFC5272, June 2008,
              <https://www.rfc-editor.org/rfc/rfc5272>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/rfc/rfc5280>.

   [RFC5911]  Hoffman, P. and J. Schaad, "New ASN.1 Modules for
              Cryptographic Message Syntax (CMS) and S/MIME", RFC 5911,
              DOI 10.17487/RFC5911, June 2010,
              <https://www.rfc-editor.org/rfc/rfc5911>.

   [RFC5958]  Turner, S., "Asymmetric Key Packages", RFC 5958,
              DOI 10.17487/RFC5958, August 2010,
              <https://www.rfc-editor.org/rfc/rfc5958>.

   [RFC8032]  Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
              Signature Algorithm (EdDSA)", RFC 8032,
              DOI 10.17487/RFC8032, January 2017,
              <https://www.rfc-editor.org/rfc/rfc8032>.

   [RFC8419]  Housley, R., "Use of Edwards-Curve Digital Signature
              Algorithm (EdDSA) Signatures in the Cryptographic Message
              Syntax (CMS)", RFC 8419, DOI 10.17487/RFC8419, August
              2018, <https://www.rfc-editor.org/rfc/rfc8419>.

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   [RFC8702]  Kampanakis, P. and Q. Dang, "Use of the SHAKE One-Way Hash
              Functions in the Cryptographic Message Syntax (CMS)",
              RFC 8702, DOI 10.17487/RFC8702, January 2020,
              <https://www.rfc-editor.org/rfc/rfc8702>.

   [X680]     ITU-T, "Information Technology - Abstract Syntax Notation
              One (ASN.1): Specification of basic notation. ITU-T
              Recommendation X.680 (2021) | ISO/IEC 8824-1:2021.",
              February 2021, <https://www.itu.int/rec/T-REC-X.680>.

Appendix A.  ASN.1 Module

   ML-DSA-Module-2024
     { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs9(9)
       id-smime(16) id-mod(0) id-mod-ml-dsa-2024(TBD) }

   DEFINITIONS IMPLICIT TAGS ::= BEGIN

   EXPORTS ALL;

   IMPORTS PUBLIC-KEY, SIGNATURE-ALGORITHM, SMIME-CAPS
     FROM AlgorithmInformation-2009 -- in [RFC5911]
     { iso(1) identified-organization(3) dod(6) internet(1)
       security(5) mechanisms(5) pkix(7) id-mod(0)
       id-mod-algorithmInformation-02(58) } ;

   --
   -- Object Identifiers
   --

   sigAlgs OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16)
       us(840) organization(1) gov(101) csor(3) nistAlgorithms(4) 3 }

   id-ml-dsa-44 OBJECT IDENTIFIER ::= { sigAlgs 17 }

   id-ml-dsa-65 OBJECT IDENTIFIER ::= { sigAlgs 18 }

   id-ml-dsa-87 OBJECT IDENTIFIER ::= { sigAlgs 19 }

   --
   -- Signature Algorithm Identifiers
   --

   sa-ml-dsa-44 SIGNATURE-ALGORITHM ::= {
     IDENTIFIER id-ml-dsa-44
     PARAMS ARE absent
     PUBLIC-KEYS { pk-ml-dsa-44 }
     SMIME-CAPS { IDENTIFIED BY id-ml-dsa-44 } }

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   sa-ml-dsa-65 SIGNATURE-ALGORITHM ::= {
     IDENTIFIER id-ml-dsa-65
     PARAMS ARE absent
     PUBLIC-KEYS { pk-ml-dsa-65 }
     SMIME-CAPS { IDENTIFIED BY id-ml-dsa-65 } }

   sa-ml-dsa-87 SIGNATURE-ALGORITHM ::= {
     IDENTIFIER id-ml-dsa-87
     PARAMS ARE absent
     PUBLIC-KEYS { pk-ml-dsa-87 }
     SMIME-CAPS { IDENTIFIED BY id-ml-dsa-87 } }

   --
   -- Public Keys
   --

   pk-ml-dsa-44 PUBLIC-KEY ::= {
     IDENTIFIER id-ml-dsa-44
     -- KEY no ASN.1 wrapping --
     CERT-KEY-USAGE
       { digitalSignature, nonRepudiation, keyCertSign, cRLSign }
     -- PRIVATE-KEY no ASN.1 wrapping -- }

   pk-ml-dsa-65 PUBLIC-KEY ::= {
     IDENTIFIER id-ml-dsa-65
     -- KEY no ASN.1 wrapping --
     CERT-KEY-USAGE
       { digitalSignature, nonRepudiation, keyCertSign, cRLSign }
     -- PRIVATE-KEY no ASN.1 wrapping -- }

   pk-ml-dsa-87 PUBLIC-KEY ::= {
     IDENTIFIER id-ml-dsa-87
     -- KEY no ASN.1 wrapping --
     CERT-KEY-USAGE
       { digitalSignature, nonRepudiation, keyCertSign, cRLSign }
     -- PRIVATE-KEY no ASN.1 wrapping -- }

   ML-DSA-PublicKey ::= OCTET STRING

   ML-DSA-PrivateKey ::= OCTET STRING

   --
   -- Expand the signature algorithm set used by CMS [RFC5911]
   --

   SignatureAlgorithmSet SIGNATURE-ALGORITHM ::= {
     sa-ml-dsa-44 |

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Internet-Draft                ML-DSA in CMS                November 2024

     sa-ml-dsa-65 |
     sa-ml-dsa-87,
     ... }

   SMimeCaps SMIME-CAPS ::= {
     sa-ml-dsa-44.&smimeCaps |
     sa-ml-dsa-65.&smimeCaps |
     sa-ml-dsa-87.&smimeCaps,
     ... }

   END

Authors' Addresses

   Ben Salter
   UK National Cyber Security Centre
   Email: ben.s3@ncsc.gov.uk

   Adam Raine
   UK National Cyber Security Centre
   Email: adam.r@ncsc.gov.uk

   Daniel Van Geest
   CryptoNext Security
   Email: daniel.vangeest@cryptonext-security.com

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