CRYSTALS-Kyber is a key encapsulation mechanism (KEM), the algorithm two parties use to agree on a shared secret key over a public channel, the same role RSA and Diffie-Hellman play in classical cryptography today. Its security rests on the hardness of the Module Learning With Errors (Module-LWE) problem, a lattice-based problem with no known efficient quantum algorithm, unlike the factoring and discrete-log problems Shor's algorithm breaks. NIST finalized Kyber as a federal standard in 2024 under the name ML-KEM (FIPS 203). It comes in three parameter sets, ML-KEM-512, -768, and -1024, trading key size and performance for security margin. Kyber is the key-exchange half of post-quantum migration; digital signatures are handled separately by algorithms such as CRYSTALS-Dilithium. Kyber keys and ciphertexts are larger than their classical RSA or ECC equivalents, which is one of the practical costs of the migration.
Related Terms
Post-Quantum Cryptography
AlgorithmsClassical cryptographic algorithms designed to be secure against attacks from both classical and quantum computers.
Shor's Algorithm
AlgorithmsA quantum algorithm for integer factorization with exponential speedup over the best known classical algorithms.
Q-Day
FundamentalsThe hypothetical point at which a quantum computer breaks currently deployed public-key cryptography.