Now this is what I like to see--life imitating Mission: Impossible, and Inspector Gadget for that matter. Computer scientists at the University of Washington have developed Vanish, software that will disappear your encrypted e-mail messages after an allotted period of time.
Once that time has passed, the software automatically re-encrypts unencrypted messages. The New York Times explains: "The pieces of the key, small numbers, tend to 'erode' over time as they gradually fall out of use. To make keys erode, or timeout, Vanish takes advantage of the structure of a peer-to-peer file system."Vanish is currently in prototype mode. To use it, both participants of the conversation must have it installed.