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

I'm not so sure about practical...

[Mithrandur]

As nice as this scheme might be compared to previous quantum cryptography schemes, there are still fundamental problemns with implementing quantum cryptography. First off, you need a single, otherwise unused optical fiber to connect the two boxes. This means running your own cable. There's really no way around that. You're not going to find unrepeated, unused fiber just lying around.

Re:I'm not so sure about practical...

[tomstdenis]

Yeah but QC mandates that this is point-to-point connections. You cannot use repeaters, routers or switches.

So the type of networking fiber that telco's do and the type that QC requires are not compatible.

[well the cables are the same, I meant the way they are laid out and used]

Tom

Re:Ah but once you know the key...

[zer0vector]

Thats a very good point. Quantum cryptography is essentially a form of One-time pad cryptography, which is an algorithm that uses a completely random assortment of characters as the key, and each key is used only once. This type of cryptography is said to be absolutely unbreakable, and in a realistic sense this is true. However, using brute force one can decode the possible message, but included with that you will get every other possible message that is of the same length as the encrypted message. This is what makes quantum cryptography so secure.