



TLS                                                              X. Song
Internet-Draft                                                 ZTE Corp.
Intended status: Informational                                   M. Chen
Expires: 25 November 2026                                   China Mobile
                                                             24 May 2026


                        Use of FN-DSA in TLS 1.3
                        draft-song-tls-fndsa-00

Abstract

   This document specifies how FN-DSA can be negotiated for
   authentication in TLS 1.3 via the signature_algorithms and
   signature_algorithms_cert extensions.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on 25 November 2026.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   2
   3.  FN-DSA Signature Scheme Values  . . . . . . . . . . . . . . .   2
     3.1.  Key and Signature Sizes . . . . . . . . . . . . . . . . .   3
     3.2.  Certificate Chain . . . . . . . . . . . . . . . . . . . .   3
     3.3.  Handshake Signature . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   FN-DSA is a lattice-based digital signature scheme based on the
   Gentry-Peikert-Vaikuntanathan (GPV) hash-and-sign framework,
   instantiated over NTRU lattices with fast Fourier sampling
   techniques.  FN-DSA offers compact signatures and public keys
   compared to other post-quantum signature schemes.  For bandwidth-
   constrained applications where signature size is a critical factor,
   FN-DSA provides a favourable alternative to ML-DSA and SLH-DSA.

   Editor's Note: The FN-DSA description of the whole text needs double
   check after FIPS206 publishment.

   This document specifies how FN-DSA is used for authentication in TLS
   1.3, including certificate chain signatures and handshake signatures
   in the CertificateVerify message.

2.  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.

3.  FN-DSA Signature Scheme Values

   As defined in [RFC8446], the SignatureScheme namespace is used for
   the negotiation of signature scheme for authentication via the
   signature_algorithms and signature_algorithms_cert extensions.  This
   document adds two new SignatureScheme values for the two FN-DSA
   parameter sets from [FIPS206] as follows.



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    +=================+=============+=================================+
    | SignatureScheme | FIPS 206    | Certificate AlgorithmIdentifier |
    +=================+=============+=================================+
    | fndsa512(TBD1)  | FN-DSA-512  | id-FN-DSA-512                   |
    |                 |             | (2.16.840.1.101.3.4.3.TBD2)     |
    +-----------------+-------------+---------------------------------+
    | fndsa1024(TBD3) | FN-DSA-1024 | id-FN-DSA-1024                  |
    |                 |             | (2.16.840.1.101.3.4.3.TBD4)     |
    +-----------------+-------------+---------------------------------+

                    Table 1: SignatureSchemes for FN-DSA

   Note that these are the pure variants of FN-DSA.  Pre-hashed variants
   are not defined in this document.  This design choice follows the
   convention established by IETF for other post-quantum signature
   algorithms in protocol bindings.  As discussed in
   [I-D.turner-lamps-cms-fn-dsa], when signature algorithms such as
   EdDSA, SLH-DSA, ML-DSA, and FN-DSA are used in protocol contexts
   where the data to be signed is typically small, the pre-hash mode
   offers no significant benefit in reducing the size of data to be
   signed.

3.1.  Key and Signature Sizes

   The following table summarizes the sizes of FN-DSA public keys and
   signatures for each parameter set, as defined in [FIPS206].  Two
   security levels of FN-DSA are recommended in this document.  FN-
   DSA-512 is expected to offer a security level equivalent to NIST
   level 1.  FN-DSA-1024 is expected to offer a security level
   equivalent to NIST level 5.

        +===============+====================+===================+
        | Parameter Set | Public Key (bytes) | Signature (bytes) |
        +===============+====================+===================+
        | FN-DSA-512    | 897                | 666               |
        +---------------+--------------------+-------------------+
        | FN-DSA-1024   | 1793               | 1280              |
        +---------------+--------------------+-------------------+

               Table 2: Key and Signature Sizes for FN-DSA

3.2.  Certificate Chain

   For the purpose of signalling support for signatures on certificates
   as per Section 4.2.3 of [RFC8446], these values indicate support for
   signing using the given AlgorithmIdentifier shown in Table 1 as
   defined in [I-D.turner-lamps-fn-dsa-certificates].




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   Implementations SHOULD validate that the public key in the end-entity
   certificate matches the expected size for the negotiated parameter
   set.  A mismatch MUST be treated as a verification failure.

3.3.  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 Section 4.4.3 of [RFC8446], and the
   corresponding end-entity certificate MUST use the corresponding
   AlgorithmIdentifier from Table 1.

   If the signature or public key is of the wrong length, the client
   MUST treat this as a verification failure, and thus terminate the
   handshake with a decrypt_error alert.

   The random salt used in FN-DSA signature generation MUST be derived
   from a cryptographically secure random number generator.  Lack of
   fresh random data during FN-DSA signature generation leads to a
   differential fault attack [BD23].

4.  Security Considerations

   The security considerations of [RFC8446] and [FIPS206] apply.

   Editor's Note: This section should be expanded with FN-DSA-specific
   security considerations, including: random number generation
   requirements (see [BD23]), floating-point arithmetic implementation
   concerns, and side-channel attack mitigations.  Specific references
   to [FIPS206] should be added once it is finalized.

5.  IANA Considerations

   This document requests new entries to the TLS SignatureScheme
   registry, according to the procedures in [RFC9847].

          +=======+=============+==============+===============+
          | Value | Description | Reconmmended | Reference     |
          +=======+=============+==============+===============+
          | TBD1  | fndsa512    | N            | This document |
          +-------+-------------+--------------+---------------+
          | TBD3  | fndsa1024   | N            | This document |
          +-------+-------------+--------------+---------------+

              Table 3: TLS SignatureScheme Values for FN-DSA






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6.  Acknowledgements

   TBD.

7.  References

7.1.  Normative References

   [FIPS206]  "Fast Fourier Transform over NTRU-Lattice-Based Digital
              Signature Algorithm", n.d., <https://www.nist.gov/news-
              events/news/2024/08/nist-releases-first-3-finalized-post-
              quantum-encryption-standards>.

   [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>.

   [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>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/rfc/rfc8446>.

7.2.  Informative References

   [BD23]     Bauer, S. and F. D. Santis, "A Differential Fault Attack
              against Deterministic Falcon Signatures", 2023,
              <https://eprint.iacr.org/2023/422>.

   [I-D.turner-lamps-cms-fn-dsa]
              Van Geest, D., Kampanakis, P., Turner, S., and B.
              Westerbaan, "Use of the FN-DSA Signature Algorithm in the
              Cryptographic Message Syntax (CMS)", Work in Progress,
              Internet-Draft, draft-turner-lamps-cms-fn-dsa-00,
              September 2025, <https://datatracker.ietf.org/doc/html/
              draft-turner-lamps-cms-fn-dsa-00>.

   [I-D.turner-lamps-fn-dsa-certificates]
              Massimo, J., "Internet X.509 Public Key Infrastructure --
              Algorithm Identifiers for the Fast-Fourier Transform over
              NTRU-Lattice-Based Digital Signature Algorithm (FN-DSA)",
              Work in Progress, Internet-Draft, draft-turner-lamps-fn-
              dsa-certificates-00, November 2025,
              <https://datatracker.ietf.org/doc/html/draft-turner-lamps-
              fn-dsa-certificates-00>.



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   [RFC9847]  Salowey, J. and S. Turner, "IANA Registry Updates for TLS
              and DTLS", RFC 9847, DOI 10.17487/RFC9847, December 2025,
              <https://www.rfc-editor.org/rfc/rfc9847>.

Authors' Addresses

   Xueyan Song
   ZTE Corp.
   Email: song.xueyan2@zte.com.cn


   Meiling Chen
   China Mobile
   Email: chenmeiling@chinamobile.com





































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