Cloudflare now uses post-quantum cryptography to talk to your origin server

This post details the rollout of X25519+Kyber768Draft00 for outbound connections from Cloudflare to origin servers and Cloudflare Workers fetch() calls. It explains the technical rationale behind adopting post-quantum cryptography (PQC) to defend against future quantum computer decryption threats. The post delves into the TLS 1.3 handshake, the role of HelloRetryRequest (HRR) in enabling smooth transitions, and the specifics of the X25519+Kyber hybrid key agreement, including the choice of security level (768 vs. 512) and the ongoing standardization of ML-KEM. It also provides quick start instructions for enabling PQC via API and configuring servers (e.g., nginx) and clients (e.g., bssl tool) for compatibility.