NCC Group: FIPS 203 Module-Lattice-Based Key-Encapsulation Mechanism Standard

FIPS 203 (Initial Public Draft) Module-Lattice-Based Key-Encapsulation Mechanism Standard written in pure Rust for server, desktop, browser and embedded applications. The source repository includes examples demonstrating benchmarking, an embedded target, constant-time statistical measurements, fuzzing, WASM execution, C FFI and Python bindings.

This crate implements the FIPS 203 draft standard in pure Rust with minimal and mainstream dependencies, and without any unsafe code. All three security parameter sets are fully supported and tested. The implementation operates in constant-time (outside of rho, which is part of the encapsulation key sent across the trust boundary in the clear), does not require the standard library, e.g. #[no_std], has no heap allocations, e.g. no alloc needed, and optionally exposes the RNG so it is suitable for the full range of applications down to the bare-metal. The API is stabilized and the code is heavily biased towards safety and correctness; further performance optimizations will be implemented as the standard matures. This crate will quickly follow any changes to FIPS 203 as they become available.

See https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.203.ipd.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 fips203::ml_kem_512; // Could also be ml_kem_768 or ml_kem_1024. 
use fips203::traits::{Decaps, Encaps, KeyGen, SerDes};

// Alice runs `try_keygen()` and then serializes the encaps key `ek` for Bob (to bytes).
let (alice_ek, alice_dk) = ml_kem_512::KG::try_keygen().unwrap();
let alice_ek_bytes = alice_ek.into_bytes();

// Alice sends the encaps key `ek_bytes` to Bob.
let bob_ek_bytes = alice_ek_bytes;

// Bob deserializes the encaps `ek_bytes` and then runs `encaps() to get the shared 
// secret `ssk` and ciphertext `ct`. He serializes the ciphertext `ct` for Alice (to bytes).
let bob_ek = ml_kem_512::EncapsKey::try_from_bytes(bob_ek_bytes).unwrap();
let (bob_ssk_bytes, bob_ct) = bob_ek.try_encaps().unwrap();
let bob_ct_bytes = bob_ct.into_bytes();

// Bob sends the ciphertext `ct_bytes` to Alice
let alice_ct_bytes = bob_ct_bytes;

// Alice deserializes the ciphertext `ct` and runs `decaps()` with her decaps key
let alice_ct = ml_kem_512::CipherText::try_from_bytes(alice_ct_bytes).unwrap();
let alice_ssk_bytes = alice_dk.try_decaps(&alice_ct).unwrap();

// Alice and Bob will now have the same secret key
assert_eq!(bob_ssk_bytes, alice_ssk_bytes);

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

Notes

• This crate is fully functional and corresponds to the first initial public draft of FIPS 203.
• Constant-time operation targets the source-code level only on MSRV, with confirmation via manual review/inspection, the embedded target, and the dudect dynamic tests.
• Note that FIPS 203 places specific requirements on randomness per section 3.3, hence the exposed RNG.
• Requires Rust 1.70 or higher. The minimum supported Rust version (MSRV) may be changed in the future, but it will be done with a minor version bump (when the major version is larger than 0).
• All on-by-default features of this library are covered by SemVer.
• The FIPS 203 draft standard and this software is experimental -- USE AT YOUR OWN RISK!

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.