Building Zero protocol for fast, secure mobile connections

This post details the development and deployment of Zero protocol, an experimental 0-RTT security protocol over TCP based on QUIC's crypto protocol. It addresses the high latency of TLS 1.2 connection establishment, particularly in emerging markets. Key technical contributions include modifications to QUIC key derivation to fix a reuse vulnerability, in-band server config rotation for efficiency, retry safety optimizations, time-bound 0-RTT data with clock skew correction, and modifications for TCP compatibility by removing explicit sequence numbers and adding an explicit length field. The post also discusses deployment considerations, including port selection and the design of the Zero RTT API within Mobile Proxygen.