TLS handshake

The TLS handshake ("handshake") is the negotiation phase that takes place at the beginning of a TLS connection. The client and server agree on the cipher suite, exchange their certificates (optional mutual authentication), and establish session keys via an ephemeral key protocol (ECDHE). TLS 1.3 reduced the handshake to 1 round-trip (versus 2 in TLS 1.2), improving the performance of signing sessions on mobile.