Just a thought. Technologists say do away with passwords, keys and cards; authenticate your identity with your voice, or your face, or your fingerprint. Great idea, right? If someone gets to know a password of yours, you can change it, but if someone works out a way to duplicate your fingerprint or voiceprint or retinal or iris ID, it seems to me you've got a big problem. There's nothing you can do. I suppose you can switch to a different finger or the other eye, but there are certain hard limits on how many times you can do that! Once you're out of fingers or eyes or whatever, you're stuck!