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Quantum encryption demo shows secure video conference potential

Cliff Saran

Quantum cryptography could be used to provide totally secure video conferences, according to Toshiba's Cambridge Research Laboratory, which demonstrated its technology at the recent business-focused showcase hosted by the Department of Trade & Industry.

Toshiba Cambridge said quantum cryptography allows users on an optical fibre network to refresh their encryption keys frequently in a completely secret way. It takes advantage of the nature of light, sending encoded single photons ("particles" of light) along standard telecom fibres.

In addition to frequent key generation, the benefit of quantum cryptography is that any attempt to break the cryptographic key by tapping into a stream of data can be detected.

Andrew Shields, group leader in research and development for quantum cryptography at Toshiba Cambridge, said the quantum approach allows cryptographic keys to be distributed securely. These are required to unscramble the encrypted message. Other approaches to encryption, such as public key infrastructure, rely on a key that is computationally difficult to crack. "Quantum is fundamentally secure," he said.

The security of quantum cryptography derives from quantum mechanics, which was devised in the early part of the 20th century and is widely used to describe processes and phenomena such as the energy level of atoms.

According to Toshiba Cambridge, the basis for quantum cryptography is that, in general, measurement alters the state of an unknown single quantum. This is why it is impossible for a third party to duplicate a key formed by quantum cryptography.

At the DTI, Toshiba Cambridge was able to show that a cryptographic key could be transmitted securely over a fibre optic cable.

The approach relies on transmitting a single photon of light to represent each binary one or zero bit in an encryption key. Because each bit is carried by a single photon, it is not possible for a hacker to tap in and remove part of the signal, Toshiba Cambridge said.

This is because a single photon cannot be split, so if a hacker measures the photons on the fibre, they will not reach the intended recipient. Only the photons that arrive at the recipient are used to form the key, so the hacker cannot gain any useful information by a "tapping" attack.

The benefit of using optical fibre is that the key can be readily changed. In the demonstration at the DTI, Toshiba Cambridge showed how each frame of video in a video conference could be secured with a new key.

"We can generate up to 100 keys per second," said Shields. This means there is no risk arising from a stored key being discovered by a would-be attacker. "It would take an enormous computational resource to crack this frame by frame," Shields added.


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