Researchers show off 'unbreakable' quantum encryption

Scientists have shown off the first commercial network with unbreakable quantum encryption and it could be available to businesses within three years.

At a conference in Vienna, researchers for the Development of a Global Network for Secure Communication based on Quantum Cryptography (SECOQC) demonstrated the system.

Rather than base the encryption on complex maths, such systems use the laws of quantum theory in particular, the Heisenberg Uncertainty Principle, which says quantum information cannot be measured without disturbing it. When used with encryption, this means that any attempt to crack the keys and access the data will be immediately obvious.

"A potential eavesdropper cannot gain any information on this key irrespective of his resources. This property which has no classical counterpart is due to the fundamental laws of quantum physics which ensure that any measurement leaves indelible traces behind. These traces manifest themselves in an error-rate that can be identified by the legitimate users," the researchers said in a statement.

The keys used to encode the data are photons, which are sent a million times a second between the nodes on the network, which in this case is based around Siemens networks, as that firm supplied the fibre network. As soon as the photons are touched they get scrambled, leaving the encryption unbroken.

The BBC attended the demonstration, and said the system detected an intruder and immediately shut itself down. It was also shown to be robust; when one link goes down, data is automatically rerouted to other connections.

Such a secure, robust system has clear benefits for businesses and governments. Dr Hannes Huebel of Vienna University, which operates one of the nodes, told the BBC: "We are constantly in touch with insurance companies and banks, and they say it's nearly better that they lose 10 million euros than if the system is down for two hours, because that might be more damaging for the bank So that's what we have to prove, that we have a reliable system that delivers quantum keys for several weeks without interruption, and then they might be more interested."

SECOQC has produced a white paper, available on its website, describing the business case for such technology, claiming: "Quantum cryptography is no more a subject reserved to scientific conferences for physics experts; it is becoming an alternative solution meeting the real needs of demanding users."