Unbreakable encryption

What is claimed to be the first commercial communication network using unbreakable encryption has been demonstrated in Vienna by a team from Bristol University and 40 other European institutions.

The technology is based on quantum cryptography — a technique that continually and randomly generates new encryption keys (codes) based on a stream of single photons emitted by a laser.

Photons have electrical fields that vibrate in different directions. The direction indicates a binary value, meaning photons are encoded with a value of 0 or 1.

The network, developed in the EU-funded SECOQC project, is installed in a standard optical fibre communication ring provided by Siemens Österreich in Vienna.

Previous developments in quantum cryptography focused on point-to-point connections between one sender and one receiver.

Although these solutions are suitable for some applications, such as connecting two data centres in metropolitan areas, there are disadvantages.

For instance, the maximum distance between sender and receiver is limited due to loss of photons in the optical fibre. The maximum speed of key generation is relatively low and comparable to that of a modem from the 1980s, and cutting the fibre or interfering with the line of sight can interrupt communication.

In a network, longer distances can be bridged, and alternative paths between sender and receiver can automatically be chosen to increase key generation throughput or prevent communication lines from being interrupted.

Also, more than two people can simultaneously obtain keys for encrypting confidential information. It is claimed the development will open up the possibility for telecom operators to develop new services and products based on quantum cryptography.