May 3, 2004 12:04 PM PDT

Quantum encryption inches closer to reality

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A team of researchers has set a speed record for a type of quantum encryption, a sign that the theoretically uncrackable system for encrypting documents could find a home commercially.

Researchers from Acadia Optronics working with the National Institute of Standards and Technology (NIST) said they have come up with a system that can transmit a stream of individual photons at a rate of 1 million bits a second. That's about 100 times faster than comparable quantum encryption systems. At that rate, it becomes practical to send encrypted video or other protected material, according to NIST.

Quantum encryption involves sending data by way of photons, the smallest unit of light. The photons are polarized, or oriented, in one of four different directions. Eavesdroppers cause detectable changes in the orientation, which in turn prevents them from getting secret information.

In the NIST-Acadia system, disturbed photons in an encryption key prevent that key from being used. The photons are time-stamped so that the intended recipient can reassemble the message and differentiate between photons from the sender versus other sources, such as the sun.

The system consists of 8-inch mirrors that transmit and receive photons, along with specially designed circuit boards.

"We are processing data much faster with this hardware than can currently be done with software," NIST engineer Alan Mink said in a statement. "You would need a computer processing at more than 100GHz to do it with software, and you still couldn't do it fast enough, because the operating system would slow you down."

A number of companies and research institutions are working on bringing this space-age form of cryptography to market. Northwestern University researchers published a paper in 2002, stating that they could send data at 250 megabits per second through quantum encryption. The Northwestern system sends streams of photons, rather than an individual string of them.

Start-up Magiq Technologies, meanwhile, has begun to sell lab equipment that combines quantum and traditional encryption methods.

Although appealing, quantum encryption is by no means a guaranteed success. For one thing, it works only over relatively short distances. Secondly, traditional encryption systems, which require that code crackers perform reams of large-number calculations, are actually quite good. Paul Kocher, president of Cryptography Research, said in a recent interview that one of the topics he doesn't lose sleep over is the quality of today's cryptography systems.


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