Quantum computers will break RSA and ECDSA. ML-KEM hybrid key exchange protects today's traffic from future "harvest now, decrypt later" attacks.
Over half of web traffic already uses X25519MLKEM768 hybrid key exchange via Chrome and Cloudflare. Is your server keeping up?
TLS 1.3 support, key exchange algorithm, forward secrecy, AEAD ciphers, certificate key type, and issuer PQC readiness.
Post-quantum cryptography is a family of algorithms designed to resist attacks from future quantum computers. In TLS the focus is quantum-safe key exchange, because encrypted traffic captured today could be decrypted later once large quantum computers exist — the 'harvest now, decrypt later' threat.
ML-KEM (FIPS 203, formerly Kyber) is the standardised post-quantum key-encapsulation mechanism. X25519MLKEM768 is a hybrid that combines classical X25519 with ML-KEM-768, so the handshake stays secure even if one component is later broken. It is the key exchange rolling out across browsers now.
Chrome 131+, Firefox 132+ and Safari 18.2+ support X25519MLKEM768, and providers such as Cloudflare plus OpenSSL 3.5 enable it server-side. A large share of TLS 1.3 traffic already negotiates hybrid PQC.
Use TLS 1.3 with a stack that supports hybrid key exchange (recent OpenSSL, BoringSSL, or a provider that enables it) and turn on X25519MLKEM768. This checker tells you whether your server negotiates it today.
Not yet for most sites — the immediate priority is hybrid key exchange, which protects against harvest-now-decrypt-later. Post-quantum signature algorithms and certificates are still being standardised and rolled out.
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