Perfect Forward Secrecy (PFS) is a property of public-key encryption systems which generate random public keys per session for the purposes of key agreement which are not based on any sort of deterministic algorithm. A compromise of one message cannot lead to the compromise of another message or multiple messages. Twitter, Apache mod_ssh, SSL, TLS, and IPSec all support forward secrecy. According to the referenced Wikipedia article: Forward secrecy is designed to prevent the compromise of a long-term secret key from affecting the confidentiality of past conversations. However, forward secrecy (including perfect forward secrecy) cannot defend against a successful cryptanalysis
