“Matthew Green and Ian Miers recently proposed puncturable forward secure encryption, which is a technique to add forward secrecy to OpenPGP-like systems. […]

Guidelines on how to approximate forward secrecy were published in 2001 by Ian Brown, Adam Back, and Ben Laurie. Although their proposal is only for an approximation of forward secrecy, it is significantly simpler than Green and Miers’ approach, and it works in practice.”