ML-KEM

ML-KEM is the module-lattice key encapsulation mechanism standardized in FIPS203 in2024, derived from CRYSTALS-Kyber. Key generation supplies an encapsulation key and a decapsulation key. Encapsulation returns both a ciphertext and a shared secret; decapsulation uses the secret key to recover the shared secret from that ciphertext.^[ref]

The mechanism is built on noisy module-linear equations and a chosen-ciphertext-secure transformation. Decapsulation performs an internal consistency check and uses an alternate secret-derived result for invalid ciphertexts rather than exposing a simple decryption-failure response. ML-KEM-512,768 and1024 are separate standardized parameter sets. Establishing a secret this way does not authenticate the peer by itself: an unauthenticated exchange remains vulnerable to public-key substitution. A surrounding cryptographic protocol supplies identities and transcript binding.