Case scenario: Alice and Bob are emailing messages back and forth between them. They know their email is not secure, so they use encryption to preserve their privacy. Suddenly, SWAT teams break simultaneously into Alice’s and Bob’s apartments. Their respective computers are seized and they are asked at gunpoint for their encryption keys. Can their prior conversation, which has been duly recorded before the break-in, remain private?
Answer: it can, but it requires a very stringent form of secrecy, which I will call Absolute Forward Secrecy (AFS). This is one step beyond Perfect Forward Secrecy (PFS), which is touted a lot these days. In this article, I discuss the different kinds of forward secrecy, and how to obtain the absolute kind with a minimum of hassle. Read More