Forward Secrecy

Forward secrecy, often called perfect forward secrecy, means that even if your long-term keys are compromised in the future, an attacker still cannot go back and decrypt your old conversations. That is usually achieved by generating short-lived session or per-message keys and destroying them after use.

The Signal Protocol supports this natively and is the best-known example. XChat may or may not use the same mechanism, but the company has not published enough technical detail to confirm it.

Why does this matter? Without forward secrecy, a stolen private key can become a master key to everything you said in the past. For ordinary users, that risk may feel remote. For people with unusually sensitive communications, it is one of the clearest lines between secure enough and seriously hardened.