I've thought about this a lot—I'm very interested in both security and privacy, so I wouldn't want to do this if I thought it would compromise either.
My current solution is that the device has three functions: encrypt/sign with private key, decrypt with private key, and send public key. They would be protected by a PIN—probably a six-digit alphanumeric pin. You might want to rate limit PIN attempts to one per second, as well.
With this scheme, I can't see how it would compromise privacy or security. No one can just scan your hand and know your identity, since you need the PIN to get your public key. And since all encryption/decryption happens on the chip, the chance that your private key gets stolen is pretty much as low as possible.
If you see any flaws with this scheme—I certainly wouldn't be surprised if there are, I just can't see any right now—please critique away!
My current solution is that the device has three functions: encrypt/sign with private key, decrypt with private key, and send public key. They would be protected by a PIN—probably a six-digit alphanumeric pin. You might want to rate limit PIN attempts to one per second, as well.
With this scheme, I can't see how it would compromise privacy or security. No one can just scan your hand and know your identity, since you need the PIN to get your public key. And since all encryption/decryption happens on the chip, the chance that your private key gets stolen is pretty much as low as possible.
If you see any flaws with this scheme—I certainly wouldn't be surprised if there are, I just can't see any right now—please critique away!