Software Design

TLS 1.2 vs TLS 1.3 Handshake Comparison

UML Sequence Diagrams · made in Skemio

Comparison sequence diagram of TLS 1.2 requiring 2 round trips versus TLS 1.3 negotiating keys in a single round trip before app data transfer.
Comparison sequence diagram of TLS 1.2 requiring 2 round trips versus TLS 1.3 negotiating keys in a single round trip before app data transfer.
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What it shows

  • TLS 1.2 needs 2 round trips to negotiate parameters before sending data
  • TLS 1.3 optimistically bundles key exchange to start data flow in 1 RTT
  • TLS 1.3 removes obsolete insecure cipher suites like RSA key transport

The takeaway

TLS 1.3 cuts handshake delay from 2-RTT to 1-RTT by eliminating legacy cipher negotiation ping-pong.

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