Forward secrecy (FS) ensures that past encrypted data remains secure even if encryption keys are compromised in the future. Itgenerates ephemeral session keys that are not reused.

Other options:

A (Tokenization) replaces sensitive data with tokens but does not prevent key compromise.

B (Key stretching) makes brute-force attacks harder but does not ensure secrecy after compromise.

D (Simultaneous Authentication of Equals – SAE) is used in WPA3 but is not related to past communication security.