Fingerprint Login

By Jerry Pournelle

January 2, 2006

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Orlando, my IBM T42P ThinkPad came with a bunch of features. One is fingerprint login. The way this works is that when you boot up, or (depending on settings) after the machine has been asleep for a while, instead of asking you to do Control-Alt-Delete and enter username and password, the system asks you to run your finger over a small optical sensor. Several users can have accounts on the machine--it recognizes whose finger that is and opens the appropriate user account.

At least that's what's supposed to happen. In practice, about half the time it doesn't recognize me at all. Sometimes it tells me to move my finger left a little. Other times it just doesnt know me at all. Usually I can manage to log in after three or so tries, but when I was out in the Mojave desert last week I never did get it to believe it was me trying to get access.

Fortunately I had the alternative of doing Control-Alt-Delete and entering my username and password.

There are two morals to this story. One is that if you use fingerprint login, make absolutely certain that you know your username and password, and that there's a way to login that way if you have to.

The other moral to this story is that technology in the real world isn't quite as reliable as it is in television dramas. The NCIS laboratories can search fingerprint databases and come up with a match every time, and they're always sure of their result. In the real world, the FBI harassed an Oregon lawyer because the Bureau was just certain that he was a match for a partial fingerprint found on one of the bombs in Madrid, even though the Spanish police had their doubts. Eventually the experts decided that their evidence fingerprint had nothing to do with the Oregon lawyer.

If my computer, with all its power, can't recognize my fingerprint half the time even though it's looking under near ideal conditions, it seems odd to be surprised to discover that the Bureau, looking with both computers and human experts, is mistaken a significant percentage of the time.

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