TLS

TLS (Transport Layer Security) is the protocol that encrypts data between client and server and verifies the server’s identity via a certificate — it is what turns HTTP into HTTPS. A handshake negotiates keys, then all traffic is encrypted.

Worked example: visiting an https:// site, your browser verifies the server’s certificate against a trusted authority, agrees on session keys, and encrypts everything after — so a network eavesdropper sees only ciphertext. Gotcha: TLS protects data IN TRANSIT, not at rest and not from a compromised endpoint; and certificate management (expiry, renewal, chain of trust) is the usual failure point — an expired cert takes a whole service offline, which is why automated renewal (ACME / Let’s Encrypt) is standard.