ML-KEM (FIPS 203): CRYSTALS-Kyber Standardized

ML-KEM (Module-Lattice-based Key Encapsulation Mechanism), standardized as FIPS 203 in August 2024, is the post-quantum replacement for Diffie-Hellman and RSA key exchange. It encapsulates a symmetric key under a public key, producing a shared secret that both parties can use for symmetric encryption. ML-KEM is derived from CRYSTALS-Kyber with minor modifications for cleaner specification.

ML-KEM defines three parameter sets. ML-KEM-512 targets approximately 128-bit classical and 100-bit post-quantum security with a public key of 800 bytes and ciphertext of 768 bytes. ML-KEM-768 targets 192-bit classical security (public key 1184 bytes, ciphertext 1088 bytes). ML-KEM-1024 targets 256-bit classical security (public key 1568 bytes, ciphertext 1568 bytes). NIST recommends ML-KEM-768 for most applications.