At 10:06 PM 1/24/03 +0100, Eugen Leitl wrote: ...

Frankly, the fingerprint is a lousy secret: you leak it all over the place. You can't help it, unless you're wearing gloves all the time. Ditto DNA.

That's generally true of biometrics. Unless taking the measurement is so intrusive it's obvious when it's taken (e.g., maybe the geometry of your sinus cavities or some such thing that requires a CAT scan to measure properly), there's no secret. People constantly seem to get themselves in trouble trying to use biometrics in a system as though they were secret. The best you can usually do is to make it moderately expensive and difficult to actually copy the biometric in a way that will fool the reader. But this is really hard. In fact, making special-purpose devices that are hard to copy or imitate is pretty difficult. It seems enormously harder to find a hard-to-copy, easy-to-use "token" that just happens to come free with a normal human body. I think the best way to think about any biometric is as a very cheap, moderately hard to copy identification token. Think of it like a good ID card that just happens to be very hard to misplace or lend to your friends. --John Kelsey, kelsey.j@ix.netcom.com