Original URL: http://www.theregister.co.uk/2002/07/17/team_demos_first_quantum_crypto/

Team demos ‘first quantum crypto prototype machine’

The secret comes out of the lab

By John Leyden

Posted in Security, 17th July 2002 16:17 GMT

Boffins have moved one step closer to a practical implementation of the Holy Grail of encryption - quantum cryptography - by exchanging keys across a 67km fibre optic network.

Until recently, the idea of quantum key distribution has been tested only in the physics laboratory. Now, a team from the University of Geneva and Swiss electronics company id Quantique have demonstrated what is described as the "first fully integrated quantum cryptography prototype machine" across a telecommunications network.

This advance is limited to fibre optic networks but other scientists are beginning to consider how quantum keys can be shared over satellite or wireless networks.

Richard Hughes and his colleagues at the Los Alamos National Laboratory, in New Mexico, and several other teams have been working on a new way to share a quantum key transmitted by photons, so that it can be exchanged over radio networks.

Hughes has no illusions about the difficulty of this task.

"One must face the much more challenging problem of transmitting the quantum key distribution (QKD) photons through the atmosphere and reliably selecting them out from the huge background of light that is present even at night," he said.

The latest steps towards developing an uncrackable code are in latest edition of the New Journal of Physics, which is published by the Institute of Physics and the German Physical Society.

Boffin note

Quantum cryptography is an advanced code-making technology which is, in principle, uncrackable. To explain this let's assume two parties Alice and Bob want to exchange a secure message across an insecure channel (e.g. the Internet), that could be being monitored by an eavesdropper, Eve.

If Alice sends her key to Bob as a series of specially ordered light particles, or photons, then the laws of quantum physics prevent Eve from being able to read the key without both Alice and Bob knowing about it.

The laws of quantum physics dictate that an eavesdropper could not measure the properties of a single photon without the risk of altering those properties. This means the legitimate receiver of a message (Bob) can test whether it has been intercepted or altered by an eavesdropper during transmission. Alice can keep discarding keys until one gets through that Eve has missed.

In contrast to methods based on codes, the keys formed by quantum cryptography can, in principle, be completely uncrackable. ®

External Links

Announcement by the Institute of Physics

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