demo · v131

X25519Kyber768 - post-quantum hybrid TLS key exchange

Chrome 131 broadly enables a hybrid TLS key exchange: classical X25519 layered with the post-quantum ML-KEM (Kyber-768). The handshake is bigger, but it defeats harvest-now-decrypt-later attacks. Pick a group below to compare the wire sizes and security properties.

handshake stats

wire size (bytes)

your own browser

probing…

the api

# Client Hello (TLS 1.3 supported_groups extension):
0x0017 (secp256r1)
0x001D (x25519)
0x6399 (X25519Kyber768Draft00)  // NEW in 131

see also