Building Zero protocol for fast, secure mobile connections

What this post added

This post details the development and deployment of Meta's experimental Zero protocol, a 0-RTT security protocol built over TCP based on QUIC's crypto protocol. It addresses the high latency of TLS 1.2 handshakes, particularly in emerging markets, by aiming for zero additional round-trip latency for security. Key technical contributions include modifications to QUIC's key derivation to prevent vulnerabilities, in-band server config rotation for efficient updates, retry safety mechanisms, time-bound 0-RTT data with clock skew correction, and adaptations for TCP by removing explicit sequence numbers and adding length fields. The post also discusses API design choices for integrating 0-RTT into Mobile Proxygen, opting for a socket API that maintains existing `connect()` and `write()` calls while introducing an `enableZeroRTT()` function.