What does PFS stand for in the context of cryptography?

In the context of cryptography, PFS stands for "Perfect Forward Secrecy." This concept ensures that session keys are not compromised even if the private key of the server is compromised in the future. It achieves this by generating unique session keys for each secure session that cannot be derived from any previous session keys or the long-term private key.

Perfect Forward Secrecy employs key exchange protocols, such as Diffie-Hellman or Elliptic Curve Diffie-Hellman, that allow two parties to establish a shared secret over an insecure channel without relying on a single long-term key. This means that even if an attacker were to record encrypted communications and later gain access to the server's private key, they would not be able to decrypt past sessions because those sessions used unique session keys.

Understanding Perfect Forward Secrecy is crucial for maintaining the confidentiality and integrity of communications, particularly in environments where security is paramount.