Also, LastPass has employed a feature called “perfect forward secrecy”. This ensures that when security keys are changed, past and future traffic also can’t be decrypted even when a particular security key is compromised.
I thought perfect forward secrecy simply gives you plausible deniability, or is that in the particular case of Off The Record messaging? How is it that a key I could have used yesterday to decrypt all the traffic I was capturing until yesterday suddely cannot be used to decrypt the same data, if none of it has changed in my vault?