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

Chrome Canary (restricted to ≤HTTP/2) if you turn on TLS 1.3 hybridized Kyber support (enable-tls13-kyber) in chrome://flags. [new!]
Our fork of Go.
BoringSSL [new!]. Upstream only supports 0x6399; for the others use our old fork.
Our fork of QUIC-go.
Goutam Tamvada's fork of Firefox.
Open Quantum Safe with the right setting. [new!]
Zig nightly. [new!]

Contact

You can reach us directly at ask-research@cloudflare.com with questions and feedback.