Information
TLS 1.3 introduces a secure session resumption mechanism using P re- S hared K eys (PSKs) that significantly improves performance for returning clients by reducing the handshake latency. This modern mechanism should be enabled to enhance user experience without compromising security.
Unlike older TLS versions, the TLS 1.3 resumption mechanism preserves P erfect F orward S ecrecy (PFS). It accomplishes this by combining the PSK with a fresh Ephemeral Diffie-Hellman key exchange (ECDHE) for every resumed session. This ensures that a compromise of the resumption key does not compromise any past or future session keys. Disabling this feature provides no security benefit and negatively impacts performance.
Solution
Ensure that ssl_session_tickets is not set to off . The recommended approach is to remove the directive entirely, as the default value is on.
If the directive is present, either remove it or set it to on :
# REMOVE this line from your configuration:
# ssl_session_tickets off;
# OR, if you want to be explicit, ensure it is set to ON (optional):
ssl_session_tickets on;
Impact:
Enabling session resumption has a positive performance impact. There are no significant negative security implications when using a TLS 1.3-only configuration.