Flipped coins with checksums
but he could have just done it
simply vocally
( 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. )
* * *