Parameter sets

Type	NIST security category	Module rank	Encapsulation key	Decapsulation key	Ciphertext	Shared secret
`MlKem512`	1	2	800 B	1,632 B	768 B	32 B
`MlKem768`	3	3	1,184 B	2,400 B	1,088 B	32 B
`MlKem1024`	5	4	1,568 B	3,168 B	1,568 B	32 B

Each type carries these sizes as constants, for example MlKem768::PUBLIC_KEY_BYTES and MlKem768::CIPHERTEXT_BYTES, and an ALGORITHM_ID string such as "ML-KEM-768".

Typed API and legacy functions

kyberlib has two surfaces over the same FIPS 203 code. New code should use the typed one.

Action	Typed `KemCore` API	Legacy free functions
Generate a key pair	`MlKem768::generate(&mut rng)?`	`kyberlib::keypair(&mut rng)?`
Encapsulate	`ek.encapsulate(&mut rng)?`	`kyberlib::encapsulate(&public, &mut rng)?`
Decapsulate	`dk.decapsulate(&ct)`, no `Result`	`kyberlib::decapsulate(&ct, &secret)?`
Secret key type	`MlKem768DecapKey`: not `Copy`, redacted `Debug`	`Keypair { public, secret }` byte arrays

The typed API enforces secret hygiene in the types. The legacy functions take and return raw byte arrays, which helps when migrating from 0.0.6 or serialising, but the caller then owns the job of not copying or logging the secret bytes. The legacy surface uses ML-KEM-768 by default and stays for compatibility.

Cargo features

Feature	Default	What it does
`kyber768`	yes	Selects ML-KEM-768 for the legacy free functions. Keep it when you turn default features off.
`std`	yes	Adds `std::error::Error` for `KyberLibError`. Turn off for `no_std`.
`kyber512`, `kyber1024`	no	Select ML-KEM-512 or ML-KEM-1024 for the legacy free functions instead. Enable at most one.
`avx2`	no	x86-64 SIMD acceleration of the polynomial arithmetic. Permits `unsafe` in the SIMD module.
`nasm`	no	The AVX2 backend assembled with NASM, for toolchains without the GNU assembler.
`hazmat`	no	Exposes the IND-CPA primitives under the KEM. Bypasses the Fujisaki-Okamoto transform: for research and testing only.
`90s`, `90s-fixslice`	no	Kyber Round 3's AES-CTR and SHA-2 variant. Not part of FIPS 203; kept for compatibility.
`fips`, `verified`	no	Placeholders for planned backends (`aws-lc-rs` and `libcrux-ml-kem`). Not implemented: enabling one does nothing yet.

The typed MlKem512, MlKem768 and MlKem1024 types work whichever parameter-set feature is on.

Authenticated key exchange

Uake (the server is authenticated) and Ake (both sides are authenticated) wrap the legacy surface in a key-exchange handshake:

use kyberlib::{keypair, Uake};

let mut alice = Uake::new();
let mut bob = Uake::new();
let bob_keys = keypair(&mut rng)?;

let client_init = alice.client_init(&bob_keys.public, &mut rng)?;
let server_send = bob.server_receive(client_init, &bob_keys.secret, &mut rng)?;
alice.client_confirm(server_send)?;

assert_eq!(alice.shared_secret, bob.shared_secret);

Crates in the workspace

Crate	What it is	On crates.io
`kyberlib`	The core library: FIPS 203 ML-KEM, `no_std` with `alloc`	Yes
`kyberlib-wasm`	`wasm-bindgen` bindings for browsers and JavaScript runtimes	Yes
`kyberlib-hybrid`	X25519MLKEM768 hybrid key exchange for TLS 1.3	Not yet
`kyberlib-pkcs8`	PKCS#8 and SubjectPublicKeyInfo encoding	Not yet: a skeleton
`kyberlib-asm`	Planned home of the SIMD backends	Not yet: a skeleton

Where is the full reference?

Every public item is documented, which the crate enforces with #![deny(missing_docs)]. The rendered reference is on docs.rs/kyberlib, and the design decisions are in the repository's architecture decision records.