Internet-Draft ML-KEM in CMS April 2025
Prat, et al. Expires 24 October 2025 [Page]
Workgroup:
LAMPS
Internet-Draft:
draft-ietf-lamps-cms-kyber-09
Published:
Intended Status:
Standards Track
Expires:
Authors:
J. Prat
CryptoNext Security
M. Ounsworth
Entrust
D. Van Geest
CryptoNext Security

Use of ML-KEM in the Cryptographic Message Syntax (CMS)

Abstract

Module-Lattice-Based Key-Encapsulation Mechanism (ML-KEM) is a quantum-resistant key-encapsulation mechanism (KEM). Three parameters sets for the ML-KEM algorithm are specified by NIST in FIPS 203. In order of increasing security strength (and decreasing performance), these parameter sets are ML-KEM-512, ML-KEM-768, and ML-KEM-1024. This document specifies the conventions for using ML-KEM with the Cryptographic Message Syntax (CMS) using the KEMRecipientInfo structure.

About This Document

This note is to be removed before publishing as an RFC.

Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ietf-lamps-cms-kyber/.

Discussion of this document takes place on the Limited Additional Mechanisms for PKIX and SMIME (lamps) 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-kyber.

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/.

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 24 October 2025.

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Table of Contents

1. Introduction

ML-KEM is an IND-CCA2-secure key-encapsulation mechanism (KEM) standardized in [FIPS203] by the US NIST PQC Project [NIST-PQ]. Prior to standardization, the algorithm was known as Kyber. ML-KEM and Kyber are not compatible.

Native support for Key Encapsulation Mechanisms (KEMs) was added to CMS in [RFC9629], which defines the KEMRecipientInfo structure for the use of KEM algorithms for the CMS enveloped-data content type, the CMS authenticated-data content type, and the CMS authenticated-enveloped-data content type. This document specifies the direct use of ML-KEM in the KEMRecipientInfo structure in CMS using each of the three parameter sets from [FIPS203], namely MK-KEM-512, ML-KEM-768, and ML-KEM-1024. It does not address or preclude the use of ML-KEM as part of any hybrid scheme.

1.1. Conventions and 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 BCP14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

1.2. ML-KEM

ML-KEM is a lattice-based key encapsulation mechanism using Module Learning with Errors as its underlying primitive, which is a structured lattices variant that offers good performance and relatively small and balanced key and ciphertext sizes. ML-KEM was standardized with three parameter sets: ML-KEM-512, ML-KEM-768, and ML-KEM-1024. The parameters for each of the security levels were chosen to be at least as secure as a generic block cipher of 128, 192, or 256 bits, respectively.

Like all KEM algorithms, ML-KEM provides three functions: KeyGen(), Encapsulate(), and Decapsulate().

KeyGen() -> (pk, sk):

Generate the public key (pk) and a private key (sk).

Encapsulate(pk) -> (ct, ss):

Given the recipient's public key (pk), produce a ciphertext (ct) to be passed to the recipient and a shared secret (ss) for use by the originator.

Decapsulate(sk, ct) -> ss:

Given the private key (sk) and the ciphertext (ct), produce the shared secret (ss) for the recipient.

The KEM functions defined above correspond to the following functions in [FIPS203]:

KeyGen():

[FIPS203] specifies two formats for an ML-KEM private key: a 64-octet seed (d,z) and an (expanded) private key, dk, which is referred to as the decapsulation key. ML-KEM.KeyGen() from section 7.1 of [FIPS203] generates the public key (ek) and dk. ML-KEM.KeyGen_internal(d,z) from section 6.1 of [FIPS203] expands the seed to ek and dk. See Section 6 of [I-D.ietf-lamps-kyber-certificates] for private key encoding considerations.

Encapsulate():

ML-KEM.Encaps(ek) from section 7.2 of [FIPS203].

Decapsulate():

ML-KEM.Decaps(dk,c) from section 7.3 of [FIPS203]. ML-KEM.KeyGen_internal(d,z) may have been used previously to expand the private key if it was encoded as a seed. See Section 8 of [I-D.ietf-lamps-kyber-certificates] for consistency considerations if the private key was stored in both seed and expanded formats.

All security levels of ML-KEM use SHA3-256, SHA3-512, SHAKE256, and SHAKE512 internally.

2. Use of the ML-KEM Algorithm in CMS

The ML-KEM algorithm MAY be employed for one or more recipients in the CMS enveloped-data content type [RFC5652], the CMS authenticated-data content type [RFC5652], or the CMS authenticated-enveloped-data content type [RFC5083]. In each case, the KEMRecipientInfo [RFC9629] is used with the ML-KEM algorithm to securely transfer the content-encryption key from the originator to the recipient.

Processing ML-KEM with KEMRecipientInfo follows the same steps as Section 2 of [RFC9629]. To support the ML-KEM algorithm, a CMS originator MUST implement the Encapsulate() function and a CMS responder MUST implement the Decapsulate() function.

2.1. RecipientInfo Conventions

When the ML-KEM algorithm is employed for a recipient, the RecipientInfo alternative for that recipient MUST be OtherRecipientInfo using the KEMRecipientInfo structure as defined in [RFC9629].

The fields of the KEMRecipientInfo MUST have the following values:

  • version is the syntax version number; it MUST be 0.

  • rid identifies the recipient's certificate or public key.

  • kem identifies the KEM algorithm; it MUST contain one of id-alg-ml-kem-512, id-alg-ml-kem-768, or id-alg-ml-kem-1024. These identifiers are reproduced in Section 3.

  • kemct is the ciphertext produced for this recipient.

  • kdf identifies the key-derivation algorithm. Note that the Key Derivation Function (KDF) used for CMS RecipientInfo process MAY be different than the KDF used within the ML-KEM algorithm.

  • kekLength is the size of the key-encryption key in octets.

  • ukm is an optional random input to the key-derivation function. ML-KEM doesn't place any requirements on the ukm contents.

  • wrap identifies a key-encryption algorithm used to encrypt the content-encryption key.

2.2. Underlying Components

When ML-KEM is employed in CMS, the security levels of the different underlying components used within the KEMRecipientInfo structure SHOULD be consistent.

2.2.1. Use of the HKDF-based Key Derivation Function

The HMAC-based Extract-and-Expand Key Derivation Function (HKDF) is defined in [RFC5869].

The HKDF function is a composition of the HKDF-Extract and HKDF-Expand functions.

HKDF(salt, IKM, info, L)
  = HKDF-Expand(HKDF-Extract(salt, IKM), info, L)

HKDF(salt, IKM, info, L) takes the following parameters:

salt:

optional salt value (a non-secret random value). In this document this parameter is unused, that is it is the zero-length string "".

IKM:

input keying material. In this document this is the shared secret outputted from the Encapsulate() or Decapsulate() functions. This corresponds to the IKM KDF input from Section 5 of [RFC9629].

info:

optional context and application specific information. In this document this corresponds to the info KDF input from Section 5 of [RFC9629]. This is the ASN.1 DER encoding of CMSORIforKEMOtherInfo which is independently generated by the sender and receiver.

L:

length of output keying material in octets. This corresponds to the L KDF input from Section 5 of [RFC9629], which is identified in the kekLength value from KEMRecipientInfo. Implementations MUST confirm that this value is consistent with the key size of the key-encryption algorithm.

HKDF may be used with different hash functions, including SHA-256 [FIPS180]. The object identifier id-alg-hkdf-with-sha256 is defined in [RFC8619], and specifies the use of HKDF with SHA-256. The parameter field MUST be absent when this algorithm identifier is used to specify the KDF for ML-KEM in KemRecipientInfo.

2.2.2. Components for ML-KEM in CMS

A compliant implementation MUST support HKDF with SHA-256, using the id-alg-hkdf-with-sha256 KDF object identifier, as the KemRecipientInfo KDF for all ML-KEM parameter sets. Note that the KDF used to process the KEMRecipientInfo structure MAY be different from the KDF used in the ML-KEM algorithm.

For ML-KEM-512, an implementation MUST support the AES-Wrap-128 [RFC3394] key-encryption algorithm using the id-aes128-wrap key-encryption algorithm object identifier [RFC3565].

For ML-KEM-768 and ML-KEM-1024, an implementation MUST support the AES-Wrap-256 [RFC3394] key-encryption algorithm using the id-aes256-wrap key-encryption algorithm object identifier [RFC3565].

The above object identifiers are reproduced for convenience in Section 3.

An implementation MAY also support other key-derivation functions and other key-encryption algorithms.

If underlying components other than those specified above are used, then the following requirements will satisfy the KDF and key wrapping algorithm requirements from Section 7 of [RFC9629]:

  • ML-KEM-512 SHOULD be used with a KDF capable of outputting a key with at least 128 bits of preimage strength and with a key wrapping algorithm with a key length of at least 128 bits.

  • ML-KEM-768 SHOULD be used with a KDF capable of outputting a key with at least 192 bits of preimage strength and with a key wrapping algorithm with a key length of at least 192 bits.

  • ML-KEM-1024 SHOULD be used with a KDF capable of outputting a key with at least 256 bits of preimage strength and with a key wrapping algorithm with a key length of at least 256 bits.

2.3. Certificate Conventions

The conventions specified in this section augment [RFC5280].

A recipient who employs the ML-KEM algorithm with a certificate MUST identify the public key in the certificate using the id-alg-ml-kem-512, id-alg-ml-kem-768, or id-alg-ml-kem-1024 object identifiers following the conventions specified in [I-D.ietf-lamps-kyber-certificates].

In particular, the key usage certificate extension MUST only contain keyEncipherment (Section 4.2.1.3 of [RFC5280]).

2.4. SMIME Capabilities Attribute Conventions

Section 2.5.2 of [RFC8551] defines the SMIMECapabilities attribute to announce a partial list of algorithms that an S/MIME implementation can support. When constructing a CMS signed-data content type [RFC5652], a compliant implementation MAY include the SMIMECapabilities attribute that announces support for one or more of the ML-KEM algorithm identifiers.

The SMIMECapability SEQUENCE representing the ML-KEM algorithm MUST include one of the ML-KEM object identifiers in the capabilityID field. When the one of the ML-KEM object identifiers appears in the capabilityID field, the parameters MUST NOT be present.

3. Identifiers

All identifiers used to indicate ML-KEM within CMS are defined elsewhere but reproduced here for convenience:

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

  id-alg-ml-kem-512 OBJECT IDENTIFIER ::= { kems 1 }

  id-alg-ml-kem-768 OBJECT IDENTIFIER ::= { kems 2 }

  id-alg-ml-kem-1024 OBJECT IDENTIFIER ::= { kems 3 }

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

  id-alg-hkdf-with-sha256 OBJECT IDENTIFIER ::= { iso(1)
      member-body(2) us(840) rsadsi(113549) pkcs(1) pkcs-9(9)
      smime(16) alg(3) 28 }

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

  id-aes128-wrap OBJECT IDENTIFIER ::= { aes 5 }
  id-aes256-wrap OBJECT IDENTIFIER ::= { aes 45 }

4. Security Considerations

The Security Considerations sections of [I-D.ietf-lamps-kyber-certificates] and [RFC9629] apply to this specification as well.

For ML-KEM-specific security considerations refer to [I-D.sfluhrer-cfrg-ml-kem-security-considerations].

The ML-KEM variant and the underlying components need to be selected consistent with the desired security level. Several security levels have been identified in NIST SP 800-57 Part 1 [NIST.SP.800-57pt1r5]. To achieve 128-bit security, ML-KEM-512 SHOULD be used, the key-derivation function SHOULD provide at least 128 bits of preimage strength, and the symmetric key-encryption algorithm SHOULD have a security strength of at least 128 bits. To achieve 192-bit security, ML-KEM-768 SHOULD be used, the key-derivation function SHOULD provide at least 192 bits of preimage strength, and the symmetric key-encryption algorithm SHOULD have a security strength of at least 192 bits. In the case of AES Key Wrap, a 256-bit key is typically used because AES-192 is not as commonly deployed. To achieve 256-bit security, ML-KEM-1024 SHOULD be used, the key-derivation function SHOULD provide at least 256 bits of preimage strength, and the symmetric key-encryption algorithm SHOULD have a security strength of at least 256 bits.

Provided all inputs are well-formed, the key establishment procedure of ML-KEM will never explicitly fail. Specifically, the ML-KEM.Encaps and ML-KEM.Decaps algorithms from [FIPS203] will always output a value with the same data type as a shared secret key, and will never output an error or failure symbol for well-formed inputs. However, it is possible (though extremely unlikely) that the process will fail in the sense that ML-KEM.Encaps and ML-KEM.Decaps will produce different outputs, even though both of them are behaving honestly and no adversarial interference is present. In this case, the sender and recipient clearly did not succeed in producing a shared secret key. This event is called a decapsulation failure. Estimates for the decapsulation failure probability (or rate) for each of the ML-KEM parameter sets are provided in Table 1 of [FIPS203] and reproduced here in Table 1.

Table 1: ML-KEM decapsulation failure rates
Parameter set Decapsulation failure rate
ML-KEM-512 2^(-138.8)
ML-KEM-768 2^(-164.8)
ML-KEM-1024 2^(-174.8)

Implementations MUST protect the ML-KEM private key, the key-encryption key, the content-encryption key, message-authentication key, and the content-authenticated-encryption key. Disclosure of the ML-KEM private key could result in the compromise of all messages protected with that key. Disclosure of the key-encryption key, the content-encryption key, or the content-authenticated-encryption key could result in compromise of the associated encrypted content. Disclosure of the key-encryption key, the message-authentication key, or the content-authenticated-encryption key could allow modification of the associated authenticated content.

Additional considerations related to key management may be found in [NIST.SP.800-57pt1r5].

The security of the ML-KEM algorithm depends on a quality random number generator. For further discussion on random number generation, see [RFC4086].

ML-KEM encapsulation and decapsulation only outputs a shared secret and ciphertext. Implementations SHOULD NOT use intermediate values directly for any purpose.

Implementations SHOULD NOT reveal information about intermediate values or calculations, whether by timing or other "side channels", otherwise an opponent may be able to determine information about the keying data and/or the recipient's private key. Although not all intermediate information may be useful to an opponent, it is preferable to conceal as much information as is practical, unless analysis specifically indicates that the information would not be useful to an opponent.

Generally, good cryptographic practice employs a given ML-KEM key pair in only one scheme. This practice avoids the risk that vulnerability in one scheme may compromise the security of the other, and may be essential to maintain provable security.

Parties MAY gain assurance that implementations are correct through formal implementation validation, such as the NIST Cryptographic Module Validation Program (CMVP) [CMVP].

5. IANA Considerations

For the ASN.1 Module in Appendix A, IANA is requested to assign an object identifier (OID) for the module identifier (TBD1) with a Description of "id-mod-cms-ml-kem-2024". The OID for the module should be allocated in the "SMI Security for S/MIME Module Identifier" registry (1.2.840.113549.1.9.16.0).

6. Acknowledgements

This document borrows heavily from [I-D.ietf-lamps-rfc5990bis], [FIPS203], and [I-D.kampanakis-ml-kem-ikev2]. Thanks go to the authors of those documents. "Copying always makes things easier and less error prone" - RFC8411.

Thanks to Carl Wallace, Jonathan Hammel, and Sean Turner for the detailed review and Carl Wallace and Philippe Cece for interoperability testing for the examples.

7. References

7.1. Normative References

[FIPS203]
"Module-lattice-based key-encapsulation mechanism standard", National Institute of Standards and Technology (U.S.), DOI 10.6028/nist.fips.203, , <https://doi.org/10.6028/nist.fips.203>.
[I-D.ietf-lamps-kyber-certificates]
Turner, S., Kampanakis, P., Massimo, J., and B. Westerbaan, "Internet X.509 Public Key Infrastructure - Algorithm Identifiers for the Module-Lattice-Based Key-Encapsulation Mechanism (ML-KEM)", Work in Progress, Internet-Draft, draft-ietf-lamps-kyber-certificates-10, , <https://datatracker.ietf.org/doc/html/draft-ietf-lamps-kyber-certificates-10>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/rfc/rfc2119>.
[RFC3394]
Schaad, J. and R. Housley, "Advanced Encryption Standard (AES) Key Wrap Algorithm", RFC 3394, DOI 10.17487/RFC3394, , <https://www.rfc-editor.org/rfc/rfc3394>.
[RFC3565]
Schaad, J., "Use of the Advanced Encryption Standard (AES) Encryption Algorithm in Cryptographic Message Syntax (CMS)", RFC 3565, DOI 10.17487/RFC3565, , <https://www.rfc-editor.org/rfc/rfc3565>.
[RFC5083]
Housley, R., "Cryptographic Message Syntax (CMS) Authenticated-Enveloped-Data Content Type", RFC 5083, DOI 10.17487/RFC5083, , <https://www.rfc-editor.org/rfc/rfc5083>.
[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, , <https://www.rfc-editor.org/rfc/rfc5280>.
[RFC5652]
Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, RFC 5652, DOI 10.17487/RFC5652, , <https://www.rfc-editor.org/rfc/rfc5652>.
[RFC5869]
Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)", RFC 5869, DOI 10.17487/RFC5869, , <https://www.rfc-editor.org/rfc/rfc5869>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8551]
Schaad, J., Ramsdell, B., and S. Turner, "Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 4.0 Message Specification", RFC 8551, DOI 10.17487/RFC8551, , <https://www.rfc-editor.org/rfc/rfc8551>.
[RFC8619]
Housley, R., "Algorithm Identifiers for the HMAC-based Extract-and-Expand Key Derivation Function (HKDF)", RFC 8619, DOI 10.17487/RFC8619, , <https://www.rfc-editor.org/rfc/rfc8619>.
[RFC9629]
Housley, R., Gray, J., and T. Okubo, "Using Key Encapsulation Mechanism (KEM) Algorithms in the Cryptographic Message Syntax (CMS)", RFC 9629, DOI 10.17487/RFC9629, , <https://www.rfc-editor.org/rfc/rfc9629>.
[X680]
ITU-T, "Information technology - Abstract Syntax Notation One (ASN.1): Specification of basic notation", ITU-T Recommendation X.680, ISO/IEC 8824-1:2021, , <https://www.itu.int/rec/T-REC-X.680>.

7.2. Informative References

[CMVP]
National Institute of Standards and Technology, "Cryptographic Module Validation Program", , <https://csrc.nist.gov/projects/cryptographic-module-validation-program>.
[FIPS180]
Dang, Q. H. and NIST, "Secure Hash Standard", NIST Federal Information Processing Standards Publications 180-4, DOI 10.6028/NIST.FIPS.180-4, , <https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf>.
[I-D.ietf-lamps-rfc5990bis]
Housley, R. and S. Turner, "Use of the RSA-KEM Algorithm in the Cryptographic Message Syntax (CMS)", Work in Progress, Internet-Draft, draft-ietf-lamps-rfc5990bis-10, , <https://datatracker.ietf.org/doc/html/draft-ietf-lamps-rfc5990bis-10>.
[I-D.kampanakis-ml-kem-ikev2]
Kampanakis, P. and G. Ravago, "Post-quantum Hybrid Key Exchange with ML-KEM in the Internet Key Exchange Protocol Version 2 (IKEv2)", Work in Progress, Internet-Draft, draft-kampanakis-ml-kem-ikev2-09, , <https://datatracker.ietf.org/doc/html/draft-kampanakis-ml-kem-ikev2-09>.
[I-D.sfluhrer-cfrg-ml-kem-security-considerations]
Fluhrer, S., Dang, Q., Mattsson, J. P., Milner, K., and D. Shiu, "ML-KEM Security Considerations", Work in Progress, Internet-Draft, draft-sfluhrer-cfrg-ml-kem-security-considerations-02, , <https://datatracker.ietf.org/doc/html/draft-sfluhrer-cfrg-ml-kem-security-considerations-02>.
[NIST-PQ]
National Institute of Standards and Technology, "Post-Quantum Cryptography Project", , <https://csrc.nist.gov/projects/post-quantum-cryptography>.
[NIST.SP.800-57pt1r5]
Barker, E. and NIST, "Recommendation for key management:part 1 - general", NIST Special Publications (General) 800-57pt1r5, DOI 10.6028/NIST.SP.800-57pt1r5, , <https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r5.pdf>.
[RFC4086]
Eastlake 3rd, D., Schiller, J., and S. Crocker, "Randomness Requirements for Security", BCP 106, RFC 4086, DOI 10.17487/RFC4086, , <https://www.rfc-editor.org/rfc/rfc4086>.
[RFC5911]
Hoffman, P. and J. Schaad, "New ASN.1 Modules for Cryptographic Message Syntax (CMS) and S/MIME", RFC 5911, DOI 10.17487/RFC5911, , <https://www.rfc-editor.org/rfc/rfc5911>.

Appendix A. ASN.1 Module

This appendix includes the ASN.1 module [X680] for ML-KEM. This module imports objects from [RFC5911], [RFC9629], [RFC8619], [I-D.ietf-lamps-kyber-certificates].

<CODE BEGINS>
CMS-ML-KEM-2024
{ iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
  pkcs-9(9) smime(16) modules(0) id-mod-cms-ml-kem-2024(TBD1) }

DEFINITIONS IMPLICIT TAGS ::= BEGIN

EXPORTS ALL;

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

  KEM-ALGORITHM
    FROM KEMAlgorithmInformation-2023  -- [RFC9629]
       { iso(1) identified-organization(3) dod(6) internet(1)
         security(5) mechanisms(5) pkix(7) id-mod(0)
         id-mod-kemAlgorithmInformation-2023(109) }

  kda-hkdf-with-sha256
    FROM HKDF-OID-2019  -- [RFC8619]
       { iso(1) member-body(2) us(840) rsadsi(113549) pkcs(1)
         pkcs-9(9) smime(16) modules(0) id-mod-hkdf-oid-2019(68) }

  kwa-aes128-wrap, kwa-aes256-wrap
    FROM CMSAesRsaesOaep-2009  -- [RFC5911]
       { iso(1) member-body(2) us(840) rsadsi(113549)
       pkcs(1) pkcs-9(9) smime(16) modules(0)
       id-mod-cms-aes-02(38) }

  id-alg-ml-kem-512, id-alg-ml-kem-768, id-alg-ml-kem-1024,
  pk-ml-kem-512, pk-ml-kem-768, pk-ml-kem-1024
    FROM X509-ML-KEM-2024 -- [I-D.ietf-lamps-kyber-certificates]
       { iso(1) identified-organization(3) dod(6)
         internet(1) security(5) mechanisms(5) pkix(7) id-mod(0)
         id-mod-x509-ml-kem-2024(TBD2) };

--
-- ML-KEM Key Encapsulation Mechanism Algorithms
--

kema-ml-kem-512 KEM-ALGORITHM ::= {
   IDENTIFIER id-alg-ml-kem-512
   PARAMS ARE absent
   PUBLIC-KEYS { pk-ml-kem-512 }
   UKM ARE optional
   SMIME-CAPS { IDENTIFIED BY id-alg-ml-kem-512 } }

kema-ml-kem-768 KEM-ALGORITHM ::= {
   IDENTIFIER id-alg-ml-kem-768
   PARAMS ARE absent
   PUBLIC-KEYS { pk-ml-kem-768 }
   UKM ARE optional
   SMIME-CAPS { IDENTIFIED BY id-alg-ml-kem-768 } }

kema-ml-kem-1024 KEM-ALGORITHM ::= {
   IDENTIFIER id-alg-ml-kem-1024
   PARAMS ARE absent
   PUBLIC-KEYS { pk-ml-kem-1024 }
   UKM ARE optional
   SMIME-CAPS { IDENTIFIED BY id-alg-ml-kem-1024 } }

-- Updates for the SMIME-CAPS Set from RFC 5911

SMimeCapsSet SMIME-CAPS ::=
   { kema-ml-kem-512.&smimeCaps |
     kema-ml-kem-768.&smimeCaps |
     kema-ml-kem-1024.&smimeCaps |
     kda-hkdf-with-sha256.&smimeCaps |
     kwa-aes128-wrap.&smimeCaps |
     kwa-aes256-wrap.&smimeCaps,
     ... }

END

<CODE ENDS>

Appendix B. Parameter Set Security and Sizes

Instead of defining the strength of a quantum algorithm in a traditional manner using the imprecise notion of bits of security, NIST has defined security levels by picking a reference scheme, which NIST expects to offer notable levels of resistance to both quantum and classical attack. To wit, a KEM algorithm that achieves NIST PQC security must require computational resources to break IND-CCA2 security comparable or greater than that required for key search on AES-128, AES-192, and AES-256 for Levels 1, 3, and 5, respectively. Levels 2 and 4 use collision search for SHA-256 and SHA-384 as reference.

Table 2: Mapping between NIST Security Level, ML-KEM parameter set, and sizes in bytes
Level Parameter Set Encap. Key Decap. Key Ciphertext Secret
1 ML-KEM-512 800 1632 768 32
3 ML-KEM-768 1184 2400 1952 32
5 ML-KEM-1024 1568 3168 2592 32

Appendix C. ML-KEM CMS Authenticated-Enveloped-Data Example

This example shows the establishment of an AES-128 content-encryption key using:

In real-world use, the originator would encrypt the content- encryption key in a manner that would allow decryption with their own private key as well as the recipient's private key. This is omitted in an attempt to simplify the example.

C.1. Originator CMS Processing

Alice obtains Bob's ML-KEM-512 public key:

-----BEGIN PUBLIC KEY-----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-----END PUBLIC KEY-----

Bob's ML-KEM-512 public key has the following key identifier:

599788C37AED400EE405D1B2A3366AB17D824A51

Alice generates a shared secret and ciphertext using Bob's ML-KEM-512 public key:

Shared secret:

7DF12D412AE299A24FDE6D7C3BB8E3194C80AD3C733DCF2775E09FE8BEDB86D8

Ciphertext:
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Alice encodes the CMSORIforKEMOtherInfo:

3010300B0609608648016503040105020110

Alice derives the key-encryption key from the shared secret and CMSORIforKEMOtherInfo using HKDF with SHA-256:

CF453A3E2BAE0A78701B8206C185A008

Alice randomly generates a 128-bit content-encryption key:

C5153005588269A0A59F3C01943FDD56

Alice uses AES-128-KEYWRAP to encrypt the content-encryption key with the key-encryption key:

C050E4392F9C14DD0AC2220203F317D701F94F9DD92778F5

Alice encrypts the padded content using AES-128-GCM with the content-encryption key and encodes the AuthEnvelopedData (using KEMRecipientInfo) and ContentInfo, and then sends the result to Bob.

The Base64-encoded result is:

-----BEGIN CMS-----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-----END CMS-----

This result decodes to:

  0 994: SEQUENCE {
  4  11:  OBJECT IDENTIFIER
       :   authEnvelopedData (1 2 840 113549 1 9 16 1 23)
 17 977:  [0] {
 21 973:   SEQUENCE {
 25   1:    INTEGER 0
 28 888:    SET {
 32 884:     [4] {
 36  11:      OBJECT IDENTIFIER '1 2 840 113549 1 9 16 13 3'
 49 867:      SEQUENCE {
 53   1:       INTEGER 0
 56  20:       [0]
       :     59 97 88 C3 7A ED 40 0E E4 05 D1 B2 A3 36 6A B1
       :     7D 82 4A 51
 78  11:       SEQUENCE {
 80   9:        OBJECT IDENTIFIER '2 16 840 1 101 3 4 4 1'
       :         }
 91 768:       OCTET STRING
       :     3E A4 0F C6 CA 09 0E 2C 8A F7 6E 27 27 AB 38 E0
       :     65 2D 95 15 98 6F E1 86 82 7F E8 4E 59 6E 42 1B
       :     85 FD 45 9C C7 89 97 37 2C 9D E3 1D 19 1B 39 C1
       :     D5 A3 EB 6D DB 56 AA DE DE 76 5C C3 90 FD BB C2
       :     F8 8C B1 75 68 1D 42 01 B8 1C CD FC B2 4F EF 13
       :     AF 2F 5A 1A BC F8 D8 AF 38 4F 02 A0 10 A6 E9 19
       :     F1 98 7A 5E 9B 1C 0E 2D 3F 07 F5 8A 9F A5 39 CE
       :     86 CC 14 99 10 A1 69 2C 0C A4 CE 0E CE 4E EE D2
       :     E6 69 9C B9 76 33 24 52 DE 4A 2E B5 CA 61 F7 B0
       :     81 33 0C 34 79 8E F7 12 A2 4E 59 C3 3C EA 1F 1F
       :     9E 6D 4F BF 37 43 A3 84 67 43 00 11 33 6F 62 D8
       :     70 79 2B 86 6B EF CD 1D 1B 36 5B ED 19 52 67 3D
       :     3A 5B 0C 20 B3 86 B4 EF D1 CF 63 FD 37 6B D4 7C
       :     CC 46 AC 4D D8 EC 66 B0 47 C4 C9 5A CF F1 CF D0
       :     28 A4 19 B0 02 FD A1 B6 17 CB A6 1D 2E 91 CF E8
       :     FF FB CB 8F FD 4D 5F 6A D8 B1 58 C2 19 E3 6D C5
       :     14 05 DC 0C 0B 23 49 79 AC 65 8E 72 BD DF 1B 67
       :     73 B9 6B 2A E3 E4 D0 7B E8 60 48 04 0C 01 67 43
       :     6F A8 39 E7 52 9B 00 CC 9A B5 5A 2F 25 DB 63 CC
       :     9F 55 75 94 E6 91 C1 1E 55 3D 4A 3E BC 76 0F 5F
       :     19 E5 FE 14 48 38 B4 C7 D1 59 1D A9 B5 D4 67 49
       :     4F D9 CA C5 2C C5 50 40 60 39 9D BD B7 22 98 EB
       :     9A 4C 01 7B 00 78 6F DC 7D 9D 7A A5 7A DB B8 B6
       :     1C 34 DE 1E 28 8B 2A B7 28 17 1D CE 14 3C D1 69
       :     53 F9 84 C1 AE D5 59 E5 6B AA 0C E6 58 D3 2C CE
       :     42 F4 40 75 04 CD 7A 57 9A D0 EF 9B 77 13 5E AA
       :     39 B6 F9 3A 3A 2E 59 97 80 7F 06 36 1C 83 F4 E6
       :     7F 8E 3F 9C F6 83 16 01 15 14 F5 D8 5A 18 1C EA
       :     D7 14 CD 49 40 E4 EB AC 01 D6 65 28 DA 32 F8 9C
       :     EA 04 28 E8 EB CA DC F8 AA 18 8C 9F 62 E8 5B 19
       :     57 65 5B 7F E2 B8 D7 97 3B 7A 72 26 B6 6D 93 BF
       :     7B 23 2F 3D CF 65 3C 84 B4 EC F1 A9 92 0D B1 94
       :     9A D7 50 B5 46 A5 55 2A 20 E5 49 09 71 9B 8C 0C
       :     07 05 6F CB 7E 57 4A D2 A3 2E C9 50 01 DD E8 44
       :     81 BE 77 D0 39 ED 5B F7 42 62 EC F3 98 1F 1B 00
       :     D3 36 6A 9C 2E 06 1C 47 E2 41 A0 61 C6 24 95 60
       :     D2 B8 44 6A 48 0C 38 C2 8B A9 89 D9 F6 8A DC 4B
       :     BA F2 A2 0B 47 E4 92 31 28 C7 23 42 D5 97 FD A2
       :     59 DE 0B 83 C2 05 6D 6B 77 E7 99 B3 19 32 4A A5
       :     0B 1D 65 9C 2A 56 02 9B 74 53 C5 F3 BA 52 43 D9
       :     FA 74 9D 91 7C 40 D9 D1 01 E4 53 BC 8B 10 E4 2A
       :     7C 08 93 23 C0 26 F7 83 E1 00 B9 FA 6E 70 14 42
       :     4D A6 FA 37 92 BC 95 7E E8 21 9D 01 6B 77 3F 28
       :     FE DC C9 62 A4 85 AB AF FE C0 23 28 19 71 E2 9A
       :     A6 89 83 9E CF D2 61 9E 92 28 7C D2 30 DB 26 A2
       :     50 7C C5 00 EB 1C 7A 52 93 B5 FE 91 7A E2 9B F1
       :     AD 35 01 24 F8 A3 11 63 52 14 B4 11 DB 9F 67 D3
       :     B8 5B D7 15 01 85 37 EA 45 B4 1F 41 B4 C6 60 51
863  13:       SEQUENCE {
865  11:        OBJECT IDENTIFIER
       :         hkdfWithSha256 (1 2 840 113549 1 9 16 3 28)
       :         }
878   1:       INTEGER 16
881  11:       SEQUENCE {
883   9:        OBJECT IDENTIFIER
       :         aes128-wrap (2 16 840 1 101 3 4 1 5)
       :         }
894  24:       OCTET STRING
       :     C0 50 E4 39 2F 9C 14 DD 0A C2 22 02 03 F3 17 D7
       :     01 F9 4F 9D D9 27 78 F5
       :        }
       :       }
       :      }
920  58:    SEQUENCE {
922   9:     OBJECT IDENTIFIER data (1 2 840 113549 1 7 1)
933  30:     SEQUENCE {
935   9:      OBJECT IDENTIFIER
       :       aes128-GCM (2 16 840 1 101 3 4 1 6)
946  17:      SEQUENCE {
948  12:       OCTET STRING 5C A5 74 68 B8 1B F0 3B 8D A7 18 6C
962   1:       INTEGER 16
       :        }
       :       }
965  13:     [0] 94 C8 68 9A 99 D2 C3 8E 19 2F A6 BA 08
       :      }
980  16:    OCTET STRING 5C F1 78 6C 57 C7 40 2B 54 FC 93 C3 0A 4A 45 33
       :     }
       :    }
       :   }

C.2. Recipient CMS Processing

Bob's ML-KEM-512 private key:

-----BEGIN PRIVATE KEY-----
MFQCAQAwCwYJYIZIAWUDBAQBBEKAQAABAgMEBQYHCAkKCwwNDg8QERITFBUWFxgZ
GhscHR4fICEiIyQlJicoKSorLC0uLzAxMjM0NTY3ODk6Ozw9Pj8=
-----END PRIVATE KEY-----

Bob decapsulates the ciphertext in the KEMRecipientInfo to get the ML-KEM-512 shared secret, encodes the CMSORIforKEMOtherInfo, derives the key-encryption key from the shared secret and the DER-encoded CMSORIforKEMOtherInfo using HKDF with SHA-256, uses AES-128-KEYWRAP to decrypt the content-encryption key with the key-encryption key, and decrypts the encrypted contents with the content-encryption key, revealing the plaintext content:

Hello, world!

Authors' Addresses

Julien Prat
CryptoNext Security
16, Boulevard Saint-Germain
75005 Paris
France
Mike Ounsworth
Entrust Limited
2500 Solandt Road -- Suite 100
Ottawa, Ontario K2K 3G5
Canada
Daniel Van Geest
CryptoNext Security
16, Boulevard Saint-Germain
75005 Paris
France