Key Exchange
Whoever wants to communicate securely, first has to generate a secret key. Can two people come up with a joint secret, even if they have never met, such that anybody who observes their entire communication does not learn the secret?!? This sounds truly magic. But as we show, it is indeed possible, and surprisingly simple. Whitfield Diffie and Martin Hellman discovered the algorithm about 50 years ago, and recently won a Turing award for their discovery. We first explain the algorithm just with colors, and then we explain it using math.