no_std compatible, pure Rust implementation of the Noise protocol framework
with support for Post Quantum (PQ) extensions as presented by
Yawning Angel, Benjamin Dowling, Andreas Hülsing, Peter Schwabe, and Fiona Johanna Weber.
Main targets of this crate are correctness, extensibility, and strict no_std compatibility
and those come with the small drawback of more verbose user experience with some boilerplate.
If you don't need PQ functionality and are developing for a regular target, you probably are better
off using these instead:
Basis of this implementation relies heavily on the abovementioned crates and I'm extending huge thanks to the developers for their effort!
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This library has not received any formal audit
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While we enable some cryptographic providers by default, it is up to you to get familiar with those and decide if they meet your security and integrity requirements
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Post-Quantum cryptography generally is not as established and mature as classical cryptography. Users are encouraged to implement hybrid encryption schemes with classical crypto primitives incorporated to provide additional security in case of a catastrophic flaw in the post-quantum algorithms. Clatter provides:
HybridHandshake- true hybrid handshake which combines both DH and KEM operations in the same handshake messages.HybridDualLayerHandshake- outer-encrypts-inner style piped handshake with cryptographic binding between the layers.DualLayerHandshake- outer-encrypts-inner style piped handshake with fully independent layers.
📖 Documentation 📖
This crate tracks Noise protocol framework revision 34. As of now we omit support for the following features:
- Handshake pattern parsing support - Handshakes have to be instantiated with the correct primitives compile-time
- Curve 448 DH support - No suitable Rust implementation exists for our requirements
- Deferred pattern support - Can be implemented by the user
- Fallback pattern support - Can be implemented by the user
This crate refers to classical Noise handshakes as NQ handshakes (non-post-quantum). But what does a PQ (post-quantum) handshake actually mean?
Key encapsulation mechanism or KEM is a public-key encryption system that allows a sender to securely transmit a short shared secret to a receiver using the receivers public key. This shared secret can then be used as a basis for further symmetric encrypted communication.
Classical Noise uses Diffie-Hellman or DH key exchanges to establish a shared secret between the parties. During a DH key exchange the shared secret is generated by both parties through mutual computations on the publicly transmitted data - whereas KEMs are used to transmit the shared secret directly.
The motivation to use KEMs lies in the fact that there are KEM algorithms that are currently thought to be secure against cryptoanalytic attacks by quantum computers. The DH algorithms used by Noise rely on the difficulty of mathematical problems that can be easily solved on a powerful quantum computer. Such quantum computers do not exist yet, but the world is already shifting towards quantum-safe cryptography.
Post Quantum Noise by Yawning Angel et al. introduced methods and rules for substituting DH key exchanges from classical Noise with KEMs, while maintaining a similar level of secrecy. This crate provides a safe Rust based implementation for the post-quantum handshakes proposed by PQNoise - so that we can keep on benefitting from the clarity and formal security guarantees of Noise even in post-quantum era.
Noise uses a simple pattern language for defining the handshake patterns. PQ patterns follow these same
rules, only substituting DH tokens with ekem and skem operations, which indicate sending of a ciphertext
that was encapsulated to the ephemeral/static key of the receiving party.
- PQNoise presents the possibility to use different KEMs for ephemeral, initiator, and responder. With Clatter the same KEM is used for both initiator and responder operations, while it is still possible to configure a separate KEM for ephemeral use.
- PQNoise presents SEEC, a method for improving RNG security in bad randomness settings. Clatter does not currently implement SEEC.
Noise uses the protocol name as a basis for the handshake hash and for this reason it is important for cross-implementation compatibility to have consistent naming schemes for the crypto primitives. For all the classical ones Noise spec defines the naming but there is no absolute source for naming the PQ ones.
On top of this, there's also the fact that Kyber KEM was renamed to "ML-KEM" during the selection process and some crypto crates still use the term "Kyber" while others have migrated to "ML-KEM". Clatter uses whichever name the underlying crate has chosen to use.
Thus Clatter proposes and uses the following naming scheme:
| Primitive | Protocol Name |
|---|---|
| Kyber 512 | Kyber512 |
| Kyber 768 | Kyber768 |
| Kyber 1024 | Kyber1024 |
| ML-KEM-512 | MLKEM512 |
| ML-KEM-768 | MLKEM768 |
| ML-KEM-1024 | MLKEM1024 |
Clatter also includes the possibility to pick different KEMs for ephemeral and static operations. If the same KEM is used for both, the name of the KEM is simply placed in the protocol name in place of the DH algorithm.
Examples:
Noise_pqNN_Kyber512_ChaChaPoly_BLAKE2s
Noise_pqNN_MLKEM512_ChaChaPoly_BLAKE2s
If, however, a different KEM is used for ephemeral and static operations, the resulting name will include both
KEMs joined together with a + symbol - ephemeral KEM first.
Examples:
Noise_pqNN_Kyber512+Kyber1024_ChaChaPoly_BLAKE2s
Noise_pqNN_MLKEM512+Kyber768_ChaChaPoly_BLAKE2s
Clatter provides ready-made hybrid handshake types. Below is the formal specification of those handshake mechanisms while the crate documentation provides practical details.
A true hybrid handshake which combines both DH and KEM operations. This handshake type accepts handshake patterns with both DH and KEM operations and mixes the results of both exchanges in a single symmetric state containing the session keys and hash, achieving true hybrid security against quantum threats while preserving the established safety guarantees of classic algorithms - all with minimal effect to the number of round trips per handshake!
Clatter provides hybrid versions of the most commonly used Noise handshake patterns in the handshakepattern
module. These hybrid pattern variables are named as noise_hybrid_<pattern>_... and are essentially combined versions of the respective
NQ and PQ handshake patterns. Each handshake interaction will complete the operations of both the NQ and PQ patterns and the hybrid
pattern is constructed in a way which preserves the relative ordering of DH and KEM operations with respect to key material transmissions.
Handshake pattern tokens e and s require special handling for sending/receiving both the DH and KEM public keys.
Clatter will always place the public DH key first in the message buffer, followed by the public KEM key. All the related
mix_hash and mix_key operations are also conducted in the same order.
If a hybrid handshake uses the same KEM for both ephemeral and static operations, the handshake name will have the following format:
Noise_hybrid<pattern>_<DH>+<KEM>_<cipher>_<hash>
If, however, a different KEM is used for ephemeral and static operations, the resulting name will include both KEMs joined
together with an additional + symbol - ephemeral KEM first:
Noise_hybrid<pattern>_<DH>+<EKEM>+<SKEM>_<cipher>_<hash>
Examples:
Noise_hybridNN_X25519+MLKEM512_ChaChaPoly_BLAKE2s
Noise_hybridNN_X25519+MLKEM512+MLKEM1024_ChaChaPoly_BLAKE2s
An outer-encrypts-inner style handshake type which first completes the outer handshake and then uses the resulting transport encryption to encrypt the inner handshake exchange. The handshakes are also cryptographically bound together so that the final transport keys will derive entropy from both handshakes.
Once the outer handshake finishes, the inner handshake completes the following Noise protocol steps:
MixHash("clatter.hybrid_dual_layer.outer")MixKeyAndHash(h_outer)
Where h_outer is the resulting handshake hash from the finalized outer handshake.
An outer-encrypts-inner style handshake type which first completes the outer handshake and then uses the resulting transport encryption to encrypt the inner handshake exchange. The handshakes are not cryptographically bound and the final transport keys only derive entropy from the inner handshake.
Warning: Use this handshake type only if you know what you are doing and absolutely require the handshake layers to remain independent.
Clatter is verified by:
- Unit tests
- Smoke tests
- Fuzzing
- Cacophony and Snow test vectors
- Supported pre-made handshake patterns verified
- Test harness in vectors/
Please see the releases page