PERFECT FORWARD SECRECY: Twitter Toughening Its Security to Thwart Government Snoops. “Perfect Forward Secrecy ensures that even if an organization recording web traffic gets access to a company’s private keys, it cannot go back and unscramble past communications all at once. Perfect Forward Secrecy encrypts each web session with an ephemeral key that is discarded once the session is over. A determined adversary could still decrypt past communications, but with Perfect Forward Secrecy the keys for each individual session would have to be cracked to read the sessions’ contents.”