Getting a Fair Toss From a Biased Coin

von Neumann is credited with coming up with the fair toss trick:<p><a href="http://en.wikipedia.org/wiki/Fair_coin#Fair_results_from_a_biased_coin" rel="nofollow">http://en.wikipedia.org/wiki/Fair_coin#Fair_results_from_a_b...</a>

Flip the coin to get sufficient entropy, then take the md5 of the bits generated. That should give you some number of virtual flips as output.

Haha! I saw the title and thought "how would I..." and reinvented it in seconds, almost (mine differed in that I'd allocate the H or T value of each pair arbitrarily by fiat ahead of time).<p>Edit: oops! I failed to reinvent discarding by pairs. That makes my attempt a fail. D'oh!

Neat idea. But how do you convince your friends to do this?<p>A: I call heads.<p>&#60;flip&#62;<p>B: It came up tails! I win!<p>A: No, wait, we're not done yet. We need to flip it again, if it comes up tails, we start over.<p>B: What? No, give me my doughnut!