Maybe it was the bong photos you and your buds sent around back in college. That Halloween you dressed up as an AK-toting mad mullah; hey, how could you know you’d be applying for security clearance today? Or that that cute guy would post those private striptease shots on Facebook? Or that your late-night rantings about what you’d read really like to do to Dick Cheneys would fester in email caches forever?

As everyone now knows, some to their great regret, information doesn’t just want to be free. It wants to stick around forever, like a digital tatoo, on hard drives, the Web, and now the cloud, and burble up and bite you at the worst moments. Even deleted data waits to be extracted with the right subpoena.

Today a UW computer-science team announced they can fix that with a tool called Vanish, which enables users to mark messages, postings, and other uploaded data to self-destruct after a certain period. It works by encrypting data with a key even the creator doesn’t have (and so can’t provide it to a con or court). At trigger time, this key breaks up and scatters in supposedly irretrievable pieces across the P2P network.

The potential unintended consequences of such a tool are enormous; any boost to privacy will be balanced against loss of accountability. Money launderers, rumor mongers, conspirators, and future Dick Cheneys may find Vanish just the thing to cover their tracks.

More info and a free prototype are available here. For now, anyway.