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Security Transport Layer Security ML-DSA FIPS204 This memo specifies how the post-quantum signature scheme ML-DSA (FIPS 204) is used for authentication in TLS 1.3. About This Document The latest revision of this draft can be found at . Status information for this document may be found at . Discussion of this document takes place on the Transport Layer Security Working Group mailing list (), which is archived at . Subscribe at . Source for this draft and an issue tracker can be found at .

Introduction The Module-Lattice-Based Digital Signature Algorithm (ML-DSA) is a post-quantum digital signature algorithm standardised by the US National Institute of Standards and Technology (NIST) in . This memo specifies how ML-DSA can be negotiated for authentication in TLS 1.3 via the signature_algorithms and signature_algorithms_cert extensions.

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 when, and only when, they appear in all capitals, as shown here.

ML-DSA SignatureScheme Values As defined in , the SignatureScheme namespace is used for the negotiation of signature scheme for authentication via the signature_algorithms and signature_algorithms_cert extensions. This document maps three new SignatureScheme values for the three ML-DSA parameter sets listed in Section 4, Table 1 of to the SignatureAlgorithmIdentifiers from as follows. SignatureSchemes for ML-DSA

SignatureScheme	FIPS 204	Signature AlgorithmIdentifier
mldsa44(0x0904)	ML-DSA-44	id-ML-DSA-44 (2.16.840.1.101.3.4.3.17)
mldsa65(0x0905)	ML-DSA-65	id-ML-DSA-65 (2.16.840.1.101.3.4.3.18)
mldsa87(0x0906)	ML-DSA-87	id-ML-DSA-87 (2.16.840.1.101.3.4.3.19)

Note that these are different from the HashML-DSA pre-hashed variants defined in Section 5.4 of , which are not used here because of the reasons laid out in .

Certificate Chain For the purpose of signalling support for signatures on certificates as per , these values indicate support for signing using the given AlgorithmIdentifier shown in as defined in .

Handshake Signature When one of those SignatureScheme values is used in a CertificateVerify message, then the signature MUST be computed and verified as specified in , using Algorithm 2 (ML-DSA.Sign) and Algorithm 3 (ML-DSA.Verify) of respectively. The context (ctx) parameter MUST be the empty string. Note that the context parameter of FIPS 204 is different from the context string of . The corresponding end-entity certificate MUST use the corresponding AlgorithmIdentifier from in its SubjectPublicKeyInfo.

Security Considerations The security considerations described in Appendices and of and apply. In particular, signature-based modes of TLS depend on the signature scheme being secure against chosen message attacks . Per Section 3.1 of , ML-DSA is designed to meet this property. Implementation failures, such as side channels, in cryptographic primitives can also compromise the primitive and thus a TLS connection depending on it. Sections 3.4 and 3.6 of discuss additional considerations for implementing ML-DSA, including guidance on the choice of hedged vs deterministic variants. These considerations apply when ML-DSA is used for TLS.

IANA Considerations This document requests new entries to the TLS SignatureScheme registry, according to the procedures in .

Value	Description	Recommended	Reference
0x0904	mldsa44	N	This document.
0x0905	mldsa65	N	This document.
0x0906	mldsa87	N	This document.

As defined in , the value N indicates

• That the item has not been evaluated by the IETF and that the IETF has made no statement about the suitability of the associated mechanism. This does not necessarily mean that the mechanism is flawed, only that no consensus exists. The IETF might have consensus to leave an item marked as "N" on the basis of the item having limited applicability or usage constraints

References Normative References This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery. This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations. Digital signatures are used within X.509 certificates and Certificate Revocation Lists (CRLs), and to sign messages. This document specifies the conventions for using FIPS 204, the Module-Lattice-Based Digital Signature Algorithm (ML-DSA) in Internet X.509 certificates and CRLs. The conventions for the associated signatures, subject public keys, and private key are also described. National Institute of Standards and Technology (U.S.) In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Informative References This document updates the changes to the TLS and DTLS IANA registries made in RFC 8447. It adds a new value, "D" for discouraged, to the "Recommended" column of the selected TLS registries and adds a "Comment" column to all active registries that do not already have a "Comment" column. Finally, it updates the registration request instructions. This document updates RFC 8447. Springer Berlin Heidelberg

Acknowledgments Thanks to Alicja Kario, John Mattsson, Rebecca Guthrie, Alexander Bokovoy, Niklas Block, Ryan Appel, Loganaden Velvindron, David Benjamin, Viktor Dukhovni, Rob Sayre, Daniel Van Geest, Martin Thomson, Wang Guilin, and Nick Sullivan for their review and feedback.