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Assuming that Bluetooth or a
similar wireless communications
protocol becomes ubiquitous in
the next few years, a small
electronic badge containing the
user's RSA (or other encryption
technology) private key. With the
push of a button, the badge would
transmit the data to a nearby
let's say). An itinerant computer
user could then read encrypted
e-mail (as with PGP) or use other
encrypted services (ssh,
whatever) without having to carry
around a floppy or a PDA
everywhere. This could also be
used to store other bits of small
information (imagine exchanging
digital business cards with a
"Wonder Twins, activate"
gesture), but I'm enamored with
secret decoder rings.
This has the obvious drawback of
relying on technology that has
not yet been deployed. It would
also be nice if a more universal
synching protocol were available.
Not wireless, not yet, but it does everything else you want. Include encryption coprocessor and JVM, comes in a ring if you want. [egnor, Jan 06 2001, last modified Oct 04 2004]
RSA, public key cryptography
The sci.crypt FAQ has a short introduction to how public key cryptosystems like RSA work. [jutta, Jan 06 2001]
|The problem with this is that your uber-sensitive Private Key is broadcast to anyone that has a bluetooth device within range.
|Bluetooth is not terribly secure. Generally this isn't an issue, but if security is important enough that you're using PGP, then Bluetooth isn't good enough without seperate layers of security. Which then raises the problem of, how do you establish a secure connection between the PC and your secret decoder ring? If you exchange public keys via Bluetooth, how do you know that Eve the eavesdropper's Bluetooth Wiretap hidden behind the bookcase isn't pretending to be your PC and giving you _its_ public key instead?
|So at the very least, you should have the PC transmit the encrypted data to your decoder ring, decode it there, and transmit it back to the PC for viewing. Eve would still be able to read your mail -- but at least she'd only get to read _that_ email, instead of being able to read every encrypted email you ever received _and_ be able to masquerade as you, like she could if she got your key.
|Ideally you'd just want the ring itself to display the data, thus avoiding sensitive information being leaked at all; but the ring doesn't really have the right form-factor for this. Personally I'd go for a smartcard: fits neatly in your wallet (something people are used to keeping safe) and has enough surface area for a small display.
|As egnor points out, the iButton uses a wired, not wireless, link... lo-tech but more secure... it also does the decryption onboard, and this can be used to authenticate (eg log in to your computer) without divulging your key, too, by using a challege-response protocol.