IntegrityChain: FIPS 204 Module-Lattice-Based Digital Signature Standard

FIPS 204 Module-Lattice-Based Digital Signature Standard written in pure Rust for server, desktop, browser and embedded applications. The source repository includes examples demonstrating benchmarking, code provenance, an embedded target, constant-time statistical measurements, a fuzzing harness, WASM execution, a C FFI shared library and Python bindings.

This crate implements the released FIPS 204 standard in pure Rust with minimal and mainstream dependencies, and without any unsafe code. All three security parameter sets are fully functional and tested. Key generation and signing are constant-time within each attempt: they do not branch on secret data, though rejection sampling makes the number of attempts vary. The crate does not require the standard library (it is #![no_std]), makes no heap allocations (no alloc needed), and exposes the RNG, so it suits the full range of applications from server down to bare metal. The API is stabilized, and the code is heavily biased towards safety and correctness.

See https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.204.pdf for a full description of the target functionality.

The functionality is extremely simple to use, as demonstrated by the following example.

// Use the desired target parameter set.
# use std::error::Error;
#
# fn main() -> Result<(), Box<dyn Error>> {
# #[cfg(all(feature = "ml-dsa-44", feature = "default-rng"))] {
use fips204::ml_dsa_44; // Could also be ml_dsa_65 or ml_dsa_87.
use fips204::traits::{SerDes, Signer, Verifier};
let message = [0u8, 1, 2, 3, 4, 5, 6, 7];

// Generate key pair and signature
let (pk1, sk) = ml_dsa_44::try_keygen()?;  // Generate both public and secret keys
let sig = sk.try_sign(&message, &[])?;  // Use the secret key to generate a message signature

// Serialize then send the public key, message and signature
let (pk_send, msg_send, sig_send) = (pk1.into_bytes(), message, sig);
let (pk_recv, msg_recv, sig_recv) = (pk_send, msg_send, sig_send);

// Deserialize the public key and signature, then verify the message
let pk2 = ml_dsa_44::PublicKey::try_from_bytes(pk_recv)?;
let v = pk2.verify(&msg_recv, &sig_recv, &[]); // Use the public key to verify the message signature
assert!(v);

// Note that the last argument to sign() and verify() is the (NIST specified) context
// value which is typically empty for basic signature generation and verification.
# }
# Ok(())
# }

The Rust Documentation lives under each Module corresponding to the desired security parameter.

Notes

• This crate is fully functional and corresponds to the final released FIPS 204 (August 13, 2024).
• Constant-time: within one attempt, key generation and signing do not branch on secret data. Two steps use rejection sampling, so their number of iterations varies: sampling the secret vectors (ExpandS), and the signing loop, which FIPS 204 restarts until a signature meets its bounds. Expanding the matrix  from the seed ρ varies too, but ρ is public, carried in the public key. Checked by source review and by the dudect measurements. The claim is at the source level: the compiler and CPU are trusted not to add secret-dependent timing, and the caller's RNG is outside it. Verify uses only public data and makes no constant-time claim.
• FIPS 204 places specific requirements on randomness (section 3.6.1), hence the exposed RNG. RNG integration uses rand_core 0.6: custom generators implement CryptoRngCore (CryptoRng + RngCore), which this crate re-exports along with RngError. Key generation and signing call try_fill_bytes, so handle its error or use the seed-based functions.
• The default features enable default-rng plus all three parameter sets. That OS RNG path is for hosted environments; it will not compile on bare-metal targets that lack a getrandom backend (for example thumbv7em-none-eabi). Embedded builds use default-features = false, the parameter-set feature they need, and the seed-based functions or *_with_rng, as in ct_cm4/: fips204 = { version = "0.5", default-features = false, features = ["ml-dsa-44"] }.
• hash_sign and hash_verify (HashML-DSA) take a precomputed digest and a DER-encoded OID (pre_hash lists the NIST CSOR encodings). The library does not hash the message. An empty OID or a digest longer than 1024 bytes is rejected.
• Test vectors: the NIST ACVP keyGen, sigGen and sigVer vectors (including HashML-DSA and private keys given as seeds), the C2SP Wycheproof ML-DSA vectors and the CCTV accumulated tests run in the test suite, and the C and Python bindings apply the ACVP files through the C ABI. The vector files stay in the repository; the published crate omits them.
• A C shared library (libfips204) for the external ML-DSA and HashML-DSA interfaces, with Python bindings, and a WASM browser demo, are described in ffi/README.md and wasm/README.md.
• Requires Rust 1.85 or higher (Debian stable, trixie). The minimum supported Rust version may change in the future, but only with a minor version bump (once the major version is above 0).
• All on-by-default features of this library are covered by SemVer.

License

Contents are licensed under either the Apache License, Version 2.0 or MIT license at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.