Practical Quantum Cryptography

Alien54 writes: "Saw this on Eureka Alert: A commercially available system for quantum key distribution and cryptography has been released by a spin-off company from the University of Geneva. The system has been tested over distances up to 70km (from Geneva to Lausanne) through standard optical fiber cables and connects to PCs via USB ports. Transmission rates of about 60 bits per seconds were achieved, sufficient for key distribution. You can see the original abstract here, which also has a link for download of the paper in PDF, Postscript, and other formats."

Comments

QC solves confidentiality, but not authentication

[The Pim]

I've heard it said that, if QC proves practical, the code-makers will have a final victory over the code-breakers. This seems true at first: there is absolutely no way, in theory, for anyone but the recipient to receive the message.

But how do you know who the recipient is? QC offers no authentication. If you have to use public key for authentication, what advantage is gained by using superior methods for confidentiality?

The only one I can think of is that, with conventional cryptography, you can capture the data stream and crack it "off-line". I suppose that this is significant: with QC you only have to worry about whether they've cracked your private key (that you will use for authentication) already, not whether they can in 100 years (because you've used it for encryption).

Another argument might be that it is easier to eavesdrop on a channel than to redirect it. But that seems like a dubious assumption, if the enemy is determined.

Thoughts?