Crate pqc_kem 

pqc-kem — Post-Quantum Key Encapsulation Mechanisms

A pure Rust, no_std-capable library implementing post-quantum KEM algorithms, meant to be imported into other builds — not built or run on its own. (For the WASM/JS bindings and the standalone .wasm artifact, see the sibling pqc-kem-wasm crate.)

• ML-KEM (NIST FIPS 203) — Primary standard, pure Rust, WASM-native

  • fips203::MlKem512Keypair — Security Level 1
  • fips203::MlKem768Keypair — Security Level 3 (recommended)
  • fips203::MlKem1024Keypair — Security Level 5
  • fips203::HybridKemKeypair — X25519 + ML-KEM-768 hybrid (primary construction)

• HQC (NIST 2025) — Code-based alternative, gated behind hqc feature. Real implementation via liboqs (native targets only, not WASM).

  • hqc::Hqc128Keypair, hqc::Hqc192Keypair, hqc::Hqc256Keypair (only compiled with --features hqc; plain code spans here, not links, so cargo doc --no-deps stays warning-free with default features, where these types do not exist)

Quick Start

use pqc_kem::fips203::HybridKemKeypair;
use rand::rngs::OsRng;

// Recipient generates keypair
let recipient = HybridKemKeypair::generate(&mut OsRng).unwrap();
let pub_key = recipient.public_key();

// Sender encapsulates
let x25519_pub = pub_key.x25519_bytes().unwrap();
let mlkem_pub = pub_key.mlkem_bytes().unwrap();
let x25519_arr: [u8; 32] = x25519_pub.try_into().unwrap();
let (ciphertext, sender_ss) = HybridKemKeypair::encapsulate(
    &mut OsRng,
    &x25519_arr,
    &mlkem_pub,
).unwrap();

// Recipient decapsulates
let recipient_ss = recipient.decapsulate(&ciphertext).unwrap();
assert_eq!(sender_ss.bytes, recipient_ss.bytes);

WASM Target Support

This crate builds cleanly as an ordinary library dependency for wasm32-unknown-unknown (e.g. from inside a wasm-bindgen/wasm-pack project of your own) — no special feature needed; the getrandom backend required for that target is wired in automatically (see Cargo.toml). It does not ship JS bindings or build as a .wasm artifact itself — that packaging lives in the sibling pqc-kem-wasm crate, which depends on this one.

no_std Support

This crate is no_std-compatible with alloc, and is always just a library — it never defines #[global_allocator] or #[panic_handler] itself (a library crate can’t validly infer from its own feature flags whether the program linking it has std elsewhere; only the final binary knows that, and only it should supply those). Disable the std feature to use the no_std path:

pqc-kem = { version = "0.2", default-features = false }

The program embedding this crate is responsible for supplying its own allocator and panic handler if it, in turn, has no std either.

---

The 0x307 crate family

pqc-kem is one of six open-source crates from 0x307, held to one audit and stability standard.

Crate	Tier	What it does
pqc-sig	Production	ML-DSA, SLH-DSA and FN-DSA signatures (FIPS 204/205/206)
pqc-kem (this crate)	Production	ML-KEM (FIPS 203), the X25519 + ML-KEM-768 hybrid, X-Wing, and sealed boxes
aethel-core	Production	Post-quantum anonymous identity: a separate identifier per context, context-bound ML-DSA signing
aethel-sdk	Preview	The SDK over aethel-core, and the place to start
aethel-vault	Preview	Agent-held wallet: policy-gated x402 / EIP-3009 signing with ML-DSA-65 spend records
pqc-privacy	Lab	Research bundle, kept off every identity and payment path

Production crates are thin, standards-bound libraries meant to be depended on today. Preview crates work and are published, with APIs still settling. Lab crates are research, never on an identity or payment path.

Runnable examples: 0x307/examples, one program per crate, pinned to the published versions.

Audit status: None of these crates has been independently audited, and none holds a CMVP / FIPS 140-3 validation. “FIPS 203/204/205/206” means the algorithms follow those standards, not that the code is certified. Known issues for this crate are in SECURITY.md. Versioning and yanks: STABILITY.md.

Re-exports

pub use error::KemError;

pub use error::KemResult;

pub use types::HybridKemCiphertext;

pub use types::HybridProfile;

pub use types::HybridPublicKey;

pub use types::KemAlgorithm;

pub use types::KemCiphertext;

pub use types::KemPublicKey;

pub use types::KemSecretKey;

pub use types::SharedSecret;

pub use fips203::HybridKemKeypair;

pub use fips203::MlKem512Keypair;

pub use fips203::MlKem768Keypair;

pub use fips203::MlKem1024Keypair;

pub use fips203::XWingKeypair;

Modules

error

Error types for all KEM operations. Unified error type for the pqc-kem crate.

fips203

ML-KEM (NIST FIPS 203) — pure Rust, WASM-native. ML-KEM (NIST FIPS 203) — Key Encapsulation Mechanism

hqc

HQC (NIST 2025 standard) — gated behind hqc feature. Real implementation via liboqs, native targets only (not WASM). HQC (Hamming Quasi-Cyclic) — NIST 2025 Standard

types

Wire types: public keys, ciphertexts, shared secrets, algorithm identifiers. Wire types for KEM public keys, ciphertexts, and shared secrets.

Constants

HYBRID_KEM_INFO

HKDF info string used in the hybrid KEM construction (profile v1).

HYBRID_PROFILE_ID

Alias for HYBRID_PROFILE_V1, kept for wire/API compatibility with existing deployments that already treat this constant as identifying PRIMARY_ALGORITHM’s hybrid construction. Points at v1, not v2 — see docs/hybrid-profiles.md for the rationale and migration guidance.

HYBRID_PROFILE_V1

Profile identifier for this crate’s original hybrid combiner (fips203::HybridKemKeypair) — wire-compatible with every prior 0.x release. HKDF-SHA256(x25519_ss ‖ mlkem_ss, info="pqc-kem-hybrid-v1"); does not bind ciphertext/public key into the KDF.

HYBRID_PROFILE_V2

Profile identifier for X-Wing (fips203::XWingKeypair, draft-connolly-cfrg-xwing-kem) — SHA3-256-based combiner that binds ct_X/pk_X. Recommended for new deployments.

PRIMARY_ALGORITHM

Algorithm suite identifier for the primary hybrid construction.

VERSION

Crate version string.