Rabin’s system, which ignited heated debates on Internet discussion groups after an article in The New York Times, is far from being implemented. In fact, Rabin has yet to even publish a paper on the idea (developed with his doctoral student Yan Zong Ding). But it’s worth thinking about because it addresses an important problem in protecting our private messages and conversations over the Internet and on mobile phones. How can we know that those systems can’t be broken? It’s true that there are plenty of ways to crack a code in addition to attacking the mathematical system that actually scrambles messages: there are plenty of potential pitfalls in implementation that may be exploited. And of course, if all else fails, you could pummel the sender or recipient until he coughs up the goods. But the mathematical formulas that make up the heart of those systems are critical, and Rabin’s idea might cast light on how to make these permanently secure.
The idea begins with a source of an unending stream of random numbers, perhaps a satellite blasting huge volumes of bits in rapid fire. So many, in fact, that it’s impossible for the most advanced storage systems imaginable to capture them all. When people want to communicate with hyper-encryption, their computers “agree” on a way to grab certain of those numbers, “like plucking raisins out of a vast pudding,” says Rabin. Those random numbers (the equivalent of the normally impractical “one time pad,” the only previous form of provably unbreakable cipher) are used to help the sender scramble the message–then the recipient uses them to help restore it to the original form. As the sender and recipient use those numbers, the computer discards them: think of the tape recording in “Mission: Impossible” when the message self-destructs. So even if a foe captures the scrambled message, then learns which pattern was used to grab numbers from the stream, the snoop won’t be able to decode the message, because the crucial random numbers from the stream will be gone.
Policy issues, such as whether unbreakable codes will give terrorists an unbeatable edge in hiding their activities, can come later, when and if hyper-encryption is put into practice. For now, “we can prove secrecy,” says Rabin, obviously delighted at going public with his brainchild.
