TLS Fundamentals

Transport Layer Security, or TLS, protects a connection across an untrusted network. An application protocol such as HTTP runs above it. TCP usually carries it, while QUIC uses the TLS 1.3 handshake with QUIC's own protected packet layer.

TLS gives a connection three main properties:

• Confidentiality: an observer cannot read protected application data without the traffic keys.
• Integrity: a peer detects protected data changed in transit.
• Authentication: a peer can prove an identity with credentials and cryptographic signatures.

These properties answer different questions. Encryption hides bytes. Integrity detects modification. Authentication tells you who controls the key used by the peer. A connection can be strongly encrypted to the wrong server if identity verification is missing.

The two working parts