Flipped coins with checksums
but he could have just done it
( Explaination: In the closing session of OSCON Mark Jason Dominus explained a clever way to perform a virtual coin toss over the telephone. He pointed out that the coin didn't have to be random to be fair -- Each side merely needs assurance that the other side can't renege and neither side knows what the other will choose. The solution used md-5/sha-1 style checksums. Difficult to exchange over a telephone without the aid of a modem.
Anyway, if two people want to make a decision by coin flip over the phone, a fair and simple way is for the parties to flip a coin on each end, and agree that if they match, person A wins, and if they differ, then person B wins. They each announce head or tails on the count of three. It's like playing rock-paper-scissors with only two outcomes, and the coins aren't even needed. )