The TLS Handshake

The TLS handshake is the negotiation that happens before any encrypted data flows.

It lets a client and server agree on encryption parameters, verify identity, and establish shared secret keys.

A TLS handshake achieves three things:

• Authentication: the client verifies the server's certificate.
• Key exchange: both sides derive shared session keys.
• Negotiation: they pick a cipher suite and protocol version.