Jack potter puts computer cryptography to work for the highest bidder: sometimes for private corporations, sometimes for the government. Sometimes the work is legal; if not, jack simply raises his price. But one day, jac...Jack potter puts computer cryptography to work for the highest bidder: sometimes for private corporations, sometimes for the government. Sometimes the work is legal; if not, jack simply raises his price. But one day, jack discovers something cloaked in the hiss of background radiation streaming past the earth from deep space: a message from an alien civilization.