Use of FN-DSA in TLS 1.3
draft-song-tls-fndsa-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Xueyan Song , Meiling Chen | ||
| Last updated | 2026-05-24 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
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| Stream | Stream state | (No stream defined) | |
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draft-song-tls-fndsa-00
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
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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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