Forward secrecy

Definition
Forward secrecy is a security technique where

"[a] system . . . develops new keys for each transaction, meaning an attacker cannot access data from previous or subsequent transactions."

Overview
"An attacker who breaches a system that provides forward secrecy can only view data from the time of the breach until the breach is discovered and rectified. Prior data remains encrypted. Additionally, under a system employing forward secrecy, session keys are destroyed after each transaction."