Perfect Forward Secrecy

Perfect Forward Secrecy (PFS) is a property of key-agreement protocols in which the compromise of long-term private keys does not compromise past session keys, ensuring that recorded encrypted communications cannot be decrypted retroactively even if an endpoint's persistent credentials are later exposed. PFS is achieved by using ephemeral keys — generated per session and discarded afterward — in protocols such as Diffie-Hellman ephemeral mode (DHE) or elliptic-curve Diffie-Hellman ephemeral mode (ECDHE). The property is essential for communications security against adversaries who store intercepted traffic in anticipation of future key compromise, a practice known as harvest