Cryptography and American Idol

The Fox TV show American Idol receives in excess of 30 million votes per week. Every Tuesday night, contestants sing, then people vote, then every Wednesday night, the results are announced. No doubt that tens of millions of people watch on Wednesday night just to hear the results, announced with great dramatic emphasis by the host.

But there’s a leak. Fox says:

Each contestant will be assigned his or her own toll-free number.

So what happens if that number is busy? In crypto/information theory talk, that is a single bit of leaked information. At time X, there were enough people calling contestant Y’s number to overwhelm the system. Chances are, if you have enough data about how often the different lines are busy, you might be able to figure out who’s winning the contest.

That’s exactly what the web site DialIdol does. First, it provides you with a free program that dials and redials your contestant’s number on your behalf. If it gets a busy signal, it reports it back to headquarters. As a result, DialIdol is predicting, with some reasonable accuracy, who’s getting kicked off.

To fix this, Fox could either use a single phone number for all votes, followed by a number entry. Alternatively, it could randomly introduce busy tones to remove the bias.

What a fantastic, everyday example of crypto and information theory at work. Even a single bit of leaked information can be extremely important.

UPDATE: Looks the real bottom 3 were among DialIdol’s bottom 4 last night. One fluke, not a bad predictor overall!