> On 09/13/2003 05:06 PM, David Wagner wrote: > > Quantum cryptography *assumes* that you > > have an authentic, untamperable channel between sender and receiver. > > Not true. The signal is continually checked for > tampering; no assumption need be made.
Quantum crypto only helps me exchange a key with whoever is on the other end of the fibre optic link. How do I know that the person I exchanged a key with is the person I wanted to exchange a key with? I don't ... unless I can make extra assumptions (such as that I have a guaranteed-authentic channel to the party I want to communicate with). If I can't make any physical assumptions about the authenticity properties of the underlying channel, I can end up with a scenario like this: I wanted to exchange a key securely with Bob, but instead, unbeknownest to me, I ended up securely exchanging key with Mallet. I believe the following is an accurate characterization: Quantum provides confidentiality (protection against eavesdropping), but only if you've already established authenticity (protection against man-in-the-middle attacks) some other way. Tell me if I got anything wrong. --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]