This came up on the Interesting article on ETI's. thread. The following article is only a step toward communications secured by quantum cryptography. As the article points out, it's not going to be commonplace any time soon. The current system, a compromise that uses quantum cryptography just to transmit the keys for unlocking coded messages, will eat up plenty of bandwidth. Right now, only communications requiring the utmost security are likely to be routed through this system.

Yet it is still a major step. Where will our civilization be a few decades or a century from now? Communications are likely to become progressively tighter and more secure.

This may possibly have implications for SETI.

Completely Secret Satellites Become Reality

By SPACE.com Staff
posted: 12:25 pm ET
30 August 2001

Hackers take your mark: Scientists at Los Alamos National Laboratory in New Mexico claim to have built a new, completely secure satellite data transfer system.

The quantum cryptography satellite system, which uses light particles in different quantum states to relay messages and that cannot be decoded by anything but the designated detector, is expected to be successful, it was reported Wednesday.

At the start of September, the researchers will test the system 6.2 miles (10 kilometers) in the air, according to New Scientist magazine. At this height, the air closely resembles the air density at 186 miles up (300 kilometers), the height which most satellites operate.

"This is a significant step towards that threshold," Tim Spiller, of the Quantum Information Processing Group at Hewlett-Packard Laboratories in the United Kingdom, told the magazine. "This group is leading the world in this area...."

The laws of quantum physics predict that interference with the data stream would disrupt it and lead to its detection. But decoding the signal would impossible without a corresponding quantum detector....

In fact, quantum cryptography may only be used to update encoded "keys" that are used to lock and unlock encrypted messages that are now sent through normal satellite links. According to the magazine, this would greatly improve the security of satellite communications but would still not guarantee total security.

However, the system could be used to generate "one time" keys that would provide absolute secrecy for individual satellite communications, although these would require significantly more bandwidth.

Cryptography expert Nigel Smart of the University of Bristol, told the magazine, "It's going to be used mainly in niche markets such as point-to-point government communications, where you need very high security."