Forward Secrecy (PFS)

A property of a key exchange mechanism where compromising the server's long-term private key does not allow decryption of previously recorded encrypted sessions. Forward secrecy is achieved by generating a unique ephemeral session key for each connection via Diffie-Hellman (DHE) or elliptic-curve Diffie-Hellman (ECDHE) key exchange. TLS 1.3 mandates forward secrecy by removing static RSA key exchange entirely. Without PFS, a single key compromise allows bulk decryption of all past traffic.