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Last Updated: Friday, 29 April, 2005, 14:20 GMT 15:20 UK
Quantum leap in secure web video
Fibre optics
The system works over fibre optic connections
Voice and video files streamed over the net could be made untappable and ultra-secure in the next few years thanks to a breakthrough by Toshiba.

Scientists at its Cambridge UK labs successfully demonstrated its Quantum Key Server system, which refreshes keys without interruption, on video.

Simply put, quantum cryptography involves encoding bits of encryption data onto particles of light - photons.

It is an emerging technology which is set to revolutionise digital security.

Current distribution methods for keys, which are needed to decrypt secure messages, are not as secure.

When data and files need to be encrypted, or made unreadable and therefore secure from prying eyes, long numeric keys - in ones and zeros - are used to scramble the data.

I sometimes say it is like the messages in Mission Impossible. If anyone tries to read the messages, they self destruct
Dr Andrew Shields, Toshiba Research
The intended recipient is able to descramble or unlock the data using another set of numbers - the key.

Applications using secure quantum cryptographic techniques are about three years away, according to Toshiba's Dr Andrew Shields, who leads the development group.

Toshiba's breakthrough showed that each frame in a video file could be encrypted using separate keys, which means that cracking one frame of a video - already difficult - would be useless unless all the other frames were cracked, too.

"The key innovation has been to make the system work continuously," Dr Shields explained to the BBC News website.

"This is important if you want to stream data like video. We can send keys, and, just by looking at them, can tell if someone has read them en route," he said.

The laws of quantum physics guarantee that the properties of the photon change if anyone intercepts it and tries to read the information from it.

"Imagine if you received a letter, you opened that letter and read it - there is no way of telling if someone has read that letter en route.

"When you encode the information on single particles, the letter self destructs whenever someone else reads it.

"I sometimes say it is like the messages in Mission Impossible. If anyone tries to read the messages, they self destruct," said Dr Shields.

The self-managing system can operate 24 hours a day, seven days a week.

It could be extended to securely encrypt other data files which require high bandwidth, such as sensitive legal documents, tax records or medical histories, added Dr Shields.

It could also be used to provide links between separate corporate sites allowing for extremely secure file transfers over fibre optic networks.

Company computer networks, where the technology will first be used, are increasingly vulnerable to the theft of keys from desktop machines.

Often this is through hacking attempts, Trojan programs deposited on computers, or malevolent employees.

Toshiba's Quantum Key Server technology would make key theft futile because it allows frequent key refreshing.

Quantum encryption will eventually give companies a "once and for all" security system, said Dr Shields.

Key changing

The safe distribution and storage of these vital keys has long been a problem for organisations. Some organisations still use human couriers to carry secret keys.

Some are stored on desktop machines which means they can be vulnerable to pilfering by hackers.

Although large amounts of computing power are required to decrypt files without keys, it is possible for an "eavesdropper" to do so.

Toshiba said it had received good feedback from government and financial institutions which were shown the demonstrations.

Now the focus is on extending the physical distance over which the technology works.

Last August, physicists successfully teleported particles of light over a distance of 600m across the River Danube in Austria.

"Teleportation" is used to describe the transfer of key properties from one particle to another without a physical link.

Dr Shields said longer distances would be achievable using repeaters, which allow for this kind of teleportation.

Long distance teleportation of photons is vital if ultra-fast and secure quantum computing is to become a reality in the future.

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