Crate lib_q_double_kem 

lib-q-double-kem (PROVISIONAL)

lib-q-double-kem provides a provisional MAUL v1 profile for combining two ML-KEM-768 encapsulation lanes into a single upgraded shared secret.

Status

• Provisional research profile for Hint-MLWE style wire-constrained transport.
• The API and wire layout can evolve before standardization.

Proof size table

Measured from tests/vectors/manifest.json (KAT seed, MAUL v1 encap path):

Scenario	Bytes	Budget	Pass
Baseline (2× ML-KEM-768)	2176	—	—
MAUL v1 wire (double_kem encap)	1260	1260	yes
Size savings vs baseline	42.1%	≥40%	yes

Fixed wire split: hint 172 B + body 1088 B = 1260 B.

KAT export

Schema: double-kem-kat-v1

cargo test -p lib-q-double-kem kat_regenerate_vectors -- --ignored

Output: tests/vectors/double-kem-v1.json

Core API

• MaulProfileV1
• double_encap
• double_decap
• ck_fo_upgrade

Shared secret derivation

The final shared secret is derived as:

ss = KDF(ss_a || ss_b)

with a domain-separated SHA3-256 based KDF.

Security notes

• This profile is intended for controlled environments and deterministic testability.
• Production integrations must review threat model fit, replay constraints, and profile governance.

Re-exports

pub use double_kem::ck_fo_upgrade;

pub use double_kem::double_decap;

pub use double_kem::double_encap;

pub use error::DoubleKemError;

pub use profile::BASELINE_DOUBLE_ML_KEM_768_CIPHERTEXT_BYTES;

pub use profile::DOUBLE_KEM_KAT_SCHEMA;

pub use profile::MAUL_HINT_BYTES;

pub use profile::MAUL_WIRE_BODY_BYTES;

pub use profile::MaulProfileV1;

pub use profile::WIRE_BUDGET_MAUL_ENCAP_BYTES;

pub use wire::MaulEncapWire;

Modules

double_kem

Core MAUL-v1 double encapsulation operations.

error

Error types for the provisional double-KEM profile.

profile

Wire/profile constants for MAUL v1 double-KEM.

wire

Wire codec for MAUL-v1 double encapsulation payload.