Kyber (ML-KEM): NIST-Standardized Post-Quantum KEM
Kyber — now officially standardized as ML-KEM (Module-Lattice-Based Key Encapsulation Mechanism) — is a post-quantum cryptographic algorithm selected by NIST in 2022 and formally published in FIPS 203 in August 2024. It is designed to replace RSA and ECDH key exchange in a future where quantum computers can break classical cryptography using Shor's algorithm.
Parameter Sets (FIPS 203)
| ML-KEM Variant | Kyber | Security | pk Size | sk Size | Ciphertext |
|---|---|---|---|---|---|
| ML-KEM-512 | Kyber-512 | 128-bit | 800 B | 1632 B | 768 B |
| ML-KEM-768 | Kyber-768 | 192-bit | 1184 B | 2400 B | 1088 B |
| ML-KEM-1024 | Kyber-1024 | 256-bit | 1568 B | 3168 B | 1568 B |
Recommended: ML-KEM-768 for most applications.
Security Analysis
| Attack | Resistance |
|---|---|
| Shor's Algorithm | Secure — no exponential speedup against lattice problems |
| Grover's Algorithm | Only quadratic speedup — 256-bit key → 128-bit effective security |
| Lattice Attacks | Best known: ~2^140 for Kyber-512 (2025 estimates) |