Function _hybrid_from_mlkem1024_p384_seed

tests/hazmat/primitives/test_hpke.py:42–51

(
    seed: bytes,
)

def _hybrid_from_mlkem1024_p384_seed(
    seed: bytes,
) -> MLKEM1024P384PrivateKey:
    # MLKEM1024-P384 seed expansion: SHAKE256(seed, 112) -> (seed_PQ (64) ||
    # seed_T (48)).
    expanded = hashlib.shake_256(seed).digest(112)
    mlkem_sk = mlkem.MLKEM1024PrivateKey.from_seed_bytes(expanded[:64])
    p384_value = int.from_bytes(expanded[64:112], "big")
    p384_sk = ec.derive_private_key(p384_value, ec.SECP384R1())
    return MLKEM1024P384PrivateKey(mlkem_sk, p384_sk)


X25519_ENC_LENGTH = 32