thumdrive integrity --Deniable Thumbdrive?

[John Bethencourt]

On Fri, Jan 24, 2003 at 09:51:46PM +0100, Thomas Shaddack wrote:
> DEFINITELY TRUE!
> 
> ...
> 
> The device should be able to perform the encryption/decryption services on
> its own (hence the cryptographic CPU). Eg, you have an untrusted computer.
> You plug the device to its port, move a document from the untrusted
> machine to device's directory "Cleartext", authorize yourself to the
> device with fingerprint and PIN, select the "Encrypt" function (which can
> be done eg. by a suffix to the PIN). In few seconds, you should then find
> the encrypted document in the device's directory "Ciphertext". Similarly,
> the device should support write-only directory, to which you could write
> files freely but won't be able to retrieve them without authorization
> (this could allow using the device for data couriers who would be able
> to pick data but won't be able to read them along the way).
>
> ...

Good points. I've thought a lot about the possibility of such devices (I
suppose they are kind of obvious/inevitable to crypto-minded people).

One comment:

One the of the primary uses for such a device would be in protocols requiring
digital signatures. If the device is to be used for this, it would seem
necessary to also include a small display on it so the user can view what the
untrusted computer wants signed and authorize the signature. Of course, with
a screen, it's going to be more like a PDA and less like a key-chain sized
device.

One of these days, I might build a little device that stores a private key
and does on-board encryption using a microcontroller. I would do it just for
fun, since it is pretty useless if the infrastructure to support it is not out
there.

John Bethencourt