RFC 9846 / START HERE
TLS 1.3 (current), before the details
TLS 1.3: updated specification
TLS means Transport Layer Security. It protects application connections, and version 1.3 uses a modern handshake to establish keys and authenticate peers.
The idea in one picture
Endpoints establish trust and keys
TLS 1.3 protects the connection
Application data travels securely
A simplified picture of the idea; the chapters explain the actual mechanisms.
Why it exists
This RFC revises the TLS 1.3 specification. The publication edition changes, but the protocol is still TLS 1.3, not TLS 1.4.
A familiar example
An HTTPS client and server establish a TLS 1.3 connection before exchanging protected web traffic.
Helpful background
You can start here without reading another RFC. If these ideas are unfamiliar, these short introductions may help.
What you’ll learn next
Begin with chapter one, or choose a topic.
- The protected handshakeTLS 1.3 negotiates keys before encrypting the remainder of the handshake.→
- Fresh key shares for each connectionA sender must not reuse its key share across multiple connections.→
- Retry stays in the transcriptHelloRetryRequest changes the offered key share without erasing the first ClientHello from the authenticated history.→
- Update before key limitsA traffic key has a finite usage bound and must be replaced before exceeding it.→
- Early data still needs replay handlingA repeated encrypted early request can cause repeated application effects.→
This introduction explains RFC 9846 (2026). Read the original RFC ↗