BBC NEWS | Technology | Quantum leap for secret codes

The BBC NEWS has a story about some exciting new breakthroughs in quantum cryptography. My friend Paul, a real crypto expert, says that this is impractical because it relies on unbroken fiber cables. I agree that the current cable-based implementation is impractical, but think of this. If you design a small powered box that can contain the photons in order (like a capacitor for light). Then you ship this box to the recipient. The photons are an encoded key for the data you will send over the net. Once the box arrives the sender and recipient will know if the key is intact because the first time it's inspected it will be altered by the fact that it was inspected. This alteration would be enough to render the key inoperable. So, once it arrives you inspect the key and use it to decrypt a test message. If the decryption works, you know that your key is OK, and you can start communicating with the sender. If the decryption of the test message fails, you know that the key has been tampered with, and the sender needs to prepare another key. Here is a quote from the article:

Contemporary encryption algorithms ensure sensitive data stays secret simply because it takes so long to work out which mathematical key was used to scramble the information. But companies could soon be turning to quantum physics to help them swap the keys they use to turn meaningful messages into scrambled characters. "It is a radically different approach to computer security," said Andrew Shields, leader of the Quantum Information Group at Toshiba's Cambridge lab where the encryption system is being developed.