FN-DSA for JOSE and COSE
draft-ietf-cose-falcon-03
| Document | Type | Active Internet-Draft (cose WG) | |
|---|---|---|---|
| Authors | Michael Prorock , Orie Steele , Hannes Tschofenig | ||
| Last updated | 2025-10-12 | ||
| Replaces | draft-ietf-cose-post-quantum-signatures | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Additional resources |
GitHub Repository
Mailing list discussion |
||
| Stream | WG state | WG Document | |
| Associated WG milestone |
|
||
| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-cose-falcon-03
CBOR Object Signing and Encryption M. Prorock
Internet-Draft mesur.io
Intended status: Standards Track O. Steele
Expires: 15 April 2026 Tradeverifyd
H. Tschofenig
H-BRS
12 October 2025
FN-DSA for JOSE and COSE
draft-ietf-cose-falcon-03
Abstract
This document specifies JSON Object Signing and Encryption (JOSE) and
CBOR Object Signing and Encryption (COSE) serializations for FFT
(fast-Fourier transform) over NTRU-Lattice-Based Digital Signature
Algorithm (FN-DSA), a Post-Quantum Cryptography (PQC) digital
signature scheme defined in US NIST FIPS 206 (expected to be
published in late 2026 early 2027).
It does not define new cryptographic primitives; rather, it specifies
how existing FN-DSA mechanisms are serialized for use in JOSE and
COSE. This document registers signature algorithms for JOSE and
COSE, specifically FN-DSA-512 and FN-DSA-1024.
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://cose-
wg.github.io/draft-ietf-cose-falcon/draft-ietf-cose-falcon.html.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ietf-cose-falcon/.
Discussion of this document takes place on the CBOR Object Signing
and Encryption Working Group mailing list (mailto:cose@ietf.org),
which is archived at https://mailarchive.ietf.org/arch/browse/cose/.
Subscribe at https://www.ietf.org/mailman/listinfo/cose/.
Source for this draft and an issue tracker can be found at
https://github.com/cose-wg/draft-ietf-cose-falcon.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Prorock, et al. Expires 15 April 2026 [Page 1]
Internet-Draft FN-DSA for JOSE and COSE October 2025
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 15 April 2026.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. The FN-DSA Algorithm Family . . . . . . . . . . . . . . . . . 4
4. FN-DSA Keys . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5.1. Validating Public Keys . . . . . . . . . . . . . . . . . 6
5.2. Side-Channel Attacks . . . . . . . . . . . . . . . . . . 6
5.3. Randomness Considerations . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6.1. New COSE Algorithms . . . . . . . . . . . . . . . . . . . 6
6.1.1. FN-DSA-512 . . . . . . . . . . . . . . . . . . . . . 6
6.1.2. FN-DSA-1024 . . . . . . . . . . . . . . . . . . . . . 6
6.2. New JOSE Algorithms . . . . . . . . . . . . . . . . . . . 7
6.2.1. FN-DSA-512 . . . . . . . . . . . . . . . . . . . . . 7
6.2.2. FN-DSA-1024 . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 10
A.1. JOSE . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Prorock, et al. Expires 15 April 2026 [Page 2]
Internet-Draft FN-DSA for JOSE and COSE October 2025
A.1.1. Key Pair . . . . . . . . . . . . . . . . . . . . . . 10
A.1.2. JSON Web Signature . . . . . . . . . . . . . . . . . 10
A.2. COSE . . . . . . . . . . . . . . . . . . . . . . . . . . 10
A.2.1. Key Pair . . . . . . . . . . . . . . . . . . . . . . 10
A.2.2. COSE Sign1 . . . . . . . . . . . . . . . . . . . . . 11
Appendix B. Document History . . . . . . . . . . . . . . . . . . 11
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 11
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
This document specifies JSON Object Signing and Encryption (JOSE) and
CBOR Object Signing and Encryption (COSE) serializations for FFT
(fast-Fourier transform) over NTRU-Lattice-Based Digital Signature
Algorithm (FN-DSA), a Post-Quantum Cryptography (PQC) digital
signature scheme defined in US NIST FIPS 206 (expected to be
published in late 2026 early 2027).
FN-DSA (formerly known as Falcon) is a lattice-based digital
signature scheme based on the GPV hash-and-sign framework [GPV08],
instantiated over NTRU lattices with fast Fourier sampling techniques
[DP16]. The core hard problem underlying FN-DSA is the SIS (Short
Integer Solution) problem over NTRU lattices.
FN-DSA (formerly known as Falcon) is a digital signature algorithm
based on lattice mathematics. It follows the hash-and-sign design
introduced by Gentry, Peikert, and Vaikuntanathan [GPV08]. FN-DSA
operates on NTRU lattices and uses fast Fourier techniques [DP16] to
make signature generation compact and efficient. The security of the
scheme relies on the hardness of solving certain lattice problems, in
particular the Short Integer Solution (SIS) problem.
FN-DSA offers:
* Post-quantum security under the assumption that NTRU-SIS remains
hard.
* Compactness in key and signature size.
* Efficient operations (roughly O(n log n)).
* A requirement for careful implementation to avoid side-channel
leakage (notably Gaussian sampling must be constant-time where
applicable).
The sizes of public key, private key, and signature for the parameter
sets are the same as in the original Falcon specification:
Prorock, et al. Expires 15 April 2026 [Page 3]
Internet-Draft FN-DSA for JOSE and COSE October 2025
+===============+==============+==============+==============+
| Parameter Set | Signature | Public Key | Private Key |
| | size (bytes) | size (bytes) | size (bytes) |
+===============+==============+==============+==============+
| FN-DSA-512 | 666 | 897 | 1281 |
+---------------+--------------+--------------+--------------+
| FN-DSA-1024 | 1280 | 1793 | 2305 |
+---------------+--------------+--------------+--------------+
Table 1
For a detailed comparison of FN-DSA with ML-DSA [USNIST.FIPS.204] and
SLH-DSA [USNIST.FIPS.205] see Section 11.3 of
[I-D.draft-ietf-pquip-pqc-engineers].
This document defines how FN-DSA is used with JSON Object Signing and
Encryption (JOSE) [RFC7515] and CBOR Object Signing and Encryption
(COSE) [RFC9052] [RFC9053].
2. 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
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. The FN-DSA Algorithm Family
The FN-DSA Signature Scheme is parameterized to support different
security levels.
This document introduces the registration of the following algorithms
in [IANA.jose]:
+=============+=============+================================+
| Name | alg | Description |
+=============+=============+================================+
| FN-DSA-512 | FN-DSA-512 | FN-DSA with parameter set 512 |
+-------------+-------------+--------------------------------+
| FN-DSA-1024 | FN-DSA-1024 | FN-DSA with parameter set 1024 |
+-------------+-------------+--------------------------------+
Table 2: JOSE Algorithms for FN-DSA
This document introduces the registration of the following algorithms
in [IANA.cose]:
Prorock, et al. Expires 15 April 2026 [Page 4]
Internet-Draft FN-DSA for JOSE and COSE October 2025
+=============+============+==========================+
| Name | alg | Description |
+=============+============+==========================+
| FN-DSA-512 | TBD1 (-54) | CBOR Object Signing |
| | | Algorithm for FALCON512 |
+-------------+------------+--------------------------+
| FN-DSA-1024 | TBD2 (-55) | CBOR Object Signing |
| | | Algorithm for FALCON1024 |
+-------------+------------+--------------------------+
Table 3: COSE Algorithms for FN-DSA
4. FN-DSA Keys
The FN-DSA Algorithm Family uses the Algorithm Key Pair (AKP) key
type, as defined in [I-D.draft-ietf-cose-dilithium].
The specific algorithms for FN-DSA, such as FALCON512 and FALCON1024,
are defined in this document and are used in the alg value of an AKP
key representation to specify the corresponding algorithm.
Thumbprints for FN-DSA keys are computed according to the process
described in [I-D.draft-ietf-cose-dilithium].
5. Security Considerations
The security considerations of [RFC7515], [RFC7517] and [RFC9053]
apply to this specification as well.
A detailed security analysis of FN-DSA is beyond the scope of this
specification; see [USNIST.FIPS.206] for additional details.
All the usual caveats for PQC and side-channel resistance apply.
* Implementations MUST ensure that alg matches the intended
algorithm variant.
* Private implementations of sampling (Gaussian, etc.) must be
constant-time to prevent leakage.
* Public keys SHOULD be validated before use (e.g., against encoding
constraints).
* Nonces, random values, blinding factors (if used) MUST originate
from a secure source of randomness.
Prorock, et al. Expires 15 April 2026 [Page 5]
Internet-Draft FN-DSA for JOSE and COSE October 2025
5.1. Validating Public Keys
TODO
5.2. Side-Channel Attacks
Implementers should follow best practices to mitigate timing, cache,
and power side channels, such as:
* Using constant-time arithmetic
* Maintaining uniform memory access patterns
* Avoiding data-dependent branching or memory indexing
5.3. Randomness Considerations
All required randomness (e.g. for signature generation) MUST be
derived from a cryptographically secure, high-entropy source.
6. IANA Considerations
6.1. New COSE Algorithms
IANA is requested to add the following entries to the COSE Algorithms
Registry. The following completed registration templates are
provided as described in [RFC9053] and [RFC9054].
6.1.1. FN-DSA-512
* Name: FN-DSA-512
* Value: TBD1 (requested assignment -54)
* Description: CBOR Object Signing Algorithm for FALCON512
* Capabilities: [kty]
* Change Controller: IETF
* Reference: RFC XXXX
* Recommended: Yes
6.1.2. FN-DSA-1024
* Name: FN-DSA-1024
Prorock, et al. Expires 15 April 2026 [Page 6]
Internet-Draft FN-DSA for JOSE and COSE October 2025
* Value: TBD2 (requested assignment -55)
* Description: CBOR Object Signing Algorithm for FALCON1024
* Capabilities: [kty]
* Change Controller: IETF
* Reference: RFC XXXX
* Recommended: Yes
6.2. New JOSE Algorithms
IANA is requested to add the following entries to the JSON Web
Signature and Encryption Algorithms Registry. The following
completed registration templates are provided as described in
[RFC7518].
6.2.1. FN-DSA-512
* Algorithm Name: FN-DSA-512
* Algorithm Description: FN-DSA-512 as described in US NIST FIPS
206.
* Algorithm Usage Location(s): alg
* JOSE Implementation Requirements: Optional
* Change Controller: IETF
* Specification Document(s): RFC XXXX
* Algorithm Analysis Documents(s): [USNIST.FIPS.206]
6.2.2. FN-DSA-1024
* Algorithm Name: FN-DSA-1024
* Algorithm Description: FN-DSA-1024 as described in US NIST FIPS
206.
* Algorithm Usage Location(s): alg
* JOSE Implementation Requirements: Optional
* Change Controller: IETF
Prorock, et al. Expires 15 April 2026 [Page 7]
Internet-Draft FN-DSA for JOSE and COSE October 2025
* Specification Document(s): RFC XXXX
* Algorithm Analysis Documents(s): [USNIST.FIPS.206]
7. References
7.1. Normative References
[I-D.draft-ietf-cose-dilithium]
Prorock, M. and O. Steele, "ML-DSA for JOSE and COSE",
Work in Progress, Internet-Draft, draft-ietf-cose-
dilithium-09, 12 September 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-cose-
dilithium-09>.
[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>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/rfc/rfc7515>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/rfc/rfc7517>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<https://www.rfc-editor.org/rfc/rfc7518>.
[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>.
[RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC9052, August 2022,
<https://www.rfc-editor.org/rfc/rfc9052>.
[RFC9053] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053,
August 2022, <https://www.rfc-editor.org/rfc/rfc9053>.
[RFC9054] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Hash Algorithms", RFC 9054, DOI 10.17487/RFC9054, August
2022, <https://www.rfc-editor.org/rfc/rfc9054>.
Prorock, et al. Expires 15 April 2026 [Page 8]
Internet-Draft FN-DSA for JOSE and COSE October 2025
[USNIST.FIPS.206]
"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>.
7.2. Informative References
[DP16] Ducas, L. and T. Prest, "Fast Fourier Orthogonalization",
Proceedings of the 2016 ACM International Symposium on
Symbolic and Algebraic Computation (ISSAC '16), pp.
191–198 , 2016, <https://doi.org/10.1145/2930889.2930923>.
[GPV08] Gentry, C., Peikert, C., and V. Vaikuntanathan, "Trapdoors
for Hard Lattices and New Cryptographic Constructions",
Proceedings of the 40th Annual ACM Symposium on Theory of
Computing (STOC '08), pp. 197–206 , 2008,
<https://doi.org/10.1145/1374376.1374407>.
[I-D.draft-ietf-pquip-pqc-engineers]
Banerjee, A., Reddy.K, T., Schoinianakis, D., Hollebeek,
T., and M. Ounsworth, "Post-Quantum Cryptography for
Engineers", Work in Progress, Internet-Draft, draft-ietf-
pquip-pqc-engineers-14, 25 August 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-pquip-
pqc-engineers-14>.
[IANA.cose]
IANA, "CBOR Object Signing and Encryption (COSE)",
<https://www.iana.org/assignments/cose>.
[IANA.jose]
IANA, "JSON Object Signing and Encryption (JOSE)",
<https://www.iana.org/assignments/jose>.
[USNIST.FIPS.204]
"Module-Lattice-Based Digital Signature Standard", n.d.,
<https://doi.org/10.6028/NIST.FIPS.204>.
[USNIST.FIPS.205]
"Stateless Hash-Based Digital Signature Standard", n.d.,
<https://doi.org/10.6028/NIST.FIPS.205>.
Prorock, et al. Expires 15 April 2026 [Page 9]
Internet-Draft FN-DSA for JOSE and COSE October 2025
Appendix A. Examples
A.1. JOSE
A.1.1. Key Pair
{
"kty": "AKP",
"alg": "FN-DSA-512",
"pub": "V53SIdVF...uvw2nuCQ",
"priv": "V53SIdVF...cDKLbsBY"
}
Figure 1: Example FN-DSA-512 Private JSON Web Key
{
"kty": "AKP",
"alg": "FN-DSA-512",
"pub": "V53SIdVF...uvw2nuCQ"
}
Figure 2: Example FN-DSA-512 Public JSON Web Key
A.1.2. JSON Web Signature
{
"kid: "clpwZ...RWYU9CUF",
"alg": "FN-DSA-512",
"typ": "JWT"
}
Figure 3: Example FN-DSA-512 Decoded Protected Header for a JSON
Web Signature
A.2. COSE
A.2.1. Key Pair
{
/ kty AKP / 1: 7,
/ alg FN-DSA-512 / 3: -54,
/ public key / -1: h'7803c0f9...3f6e2c70',
/ private key / -2: h'7803c0f9...3bba7abd'
}
Figure 4: Example FN-DSA-512 Private COSE Key
Prorock, et al. Expires 15 April 2026 [Page 10]
Internet-Draft FN-DSA for JOSE and COSE October 2025
{
/ kty AKP / 1: 7,
/ alg FN-DSA-512 / 3: -54,
/ public key / -1: h'7803c0f9...3f6e2c70',
}
Figure 5: Example FN-DSA-512 Public COSE Key
A.2.2. COSE Sign1
18([
<<{
/ alg FN-DSA-512 / 1: -54,
}>>,
/ unprotected / {},
/ payload / h'66616b65',
/ signature / h'53e855e8...0f263549'
])
Figure 6: Example FN-DSA-512 COSE Sign1
Appendix B. Document History
-02
* Converted to markdown
* Applied feedback from IESG Evaluation on ML-DSA
* Revised references
* Revised abstract
-01
* Added Acknowledgements
* Added Document History
* Updated test vectors
Acknowledgments
We would like to especially thank David Balenson for careful review
of approaches taken in this document. We would also like to thank
Michael B. Jones for guidance in authoring.
Prorock, et al. Expires 15 April 2026 [Page 11]
Internet-Draft FN-DSA for JOSE and COSE October 2025
Contributors
Rafael Misoczki
Google
Email: rafaelmisoczki@google.com
Michael Osborne
IBM
Email: osb@zurich.ibm.com
Christine Cloostermans
NXP
Email: christine.cloostermans@nxp.com
Authors' Addresses
Michael Prorock
mesur.io
Email: mprorock@mesur.io
Orie Steele
Tradeverifyd
Email: orie@or13.io
Hannes Tschofenig
University of Applied Sciences Bonn-Rhein-Sieg
Germany
Email: hannes.tschofenig@gmx.net
Prorock, et al. Expires 15 April 2026 [Page 12]