Cloudflare Research: Post-Quantum Key Agreement

On essentially all domains served through Cloudflare, including this one, we have enabled hybrid post-quantum key agreement. Read our blog for the details.

You are using X25519 which is not post-quantum secure.

Deployed key agreements

Available with TLSv1.3 including HTTP/3 (QUIC)

Key agreement TLS identifier
X25519Kyber512Draft00 0xfe30
X25519Kyber768Draft00 0x6399 (recommended) and 0xfe31 (obsolete)
X25519Kyber[x]Draft00 is a hybrid of X25519 and Kyber[x]Draft00 (in that order).

Client support


You can reach us directly at with questions and feedback.