TLS 1.3 Protocol

RFC 8446 defines Transport Layer Security Version 1.3, delivering major security and performance improvements over previous TLS versions.

Key Improvements in TLS 1.3

1. 1-RTT Handshake: Halves handshake latency compared to TLS 1.2 by guessing the key exchange algorithm in the initial ClientHello.
2. Removed Deprecated Primitives: Obsoletes static RSA key exchange, Diffie-Hellman static groups, SHA-1, MD5, and CBC ciphers in favor of Ephemeral Diffie-Hellman (ECDHE) with AEAD ciphers.
3. Encrypted Handshake: Certificate messages and extensions are encrypted immediately following the ServerHello.
4. Resumption (0-RTT): Pre-shared key resumption allows early data transmission on the very first round trip.

Handshake Diagram

Client                                               Server
ClientHello (KeyShare, SNI, ALPN) -------->
                                              ServerHello (KeyShare)
                                              {EncryptedExtensions}
                                              {Certificate}
                                              {CertificateVerify}
                                  <--------   {Finished}
{Finished}                        -------->
[Application Data]                <------->   [Application Data]

Related

• Protocol: TLS 1.2
• Guide: TLS
• Security: TLS