By Roland Piquepaille
If you use a webcam to talk with your mom, this tool is not for you. But if you're working for a company and that you have to routinely discuss about sensitive future projects or the possible acquisition of another company, you need more security, and this new video conferencing system based on quantum cryptography is a tool you need. According to this article from Nature, researchers from Toshiba have developed a system which can generate 100 quantum 'keys' every second, fast enough to protect every frame in a video exchange. This technology, which today is working over a distance of about 120 kilometers, could become commercially available within two years at an initial cost of $20,000. Read more...Here is the introduction from Nature.
Scientists from Toshiba's Cambridge Research Laboratory unveiled their invention to business leaders and government officials at Britain's Department of Trade and Industry in London on 27 April.
Their system is capable of generating 100 quantum 'keys' every second. This is fast enough for every individual frame of video to be protected by its own encryption. "This makes the system highly secure," says Andrew Shields, who leads the Cambridge team. "It would take an enormous computational resource to crack this frame by frame."
Of course, today's videoconferencing tools using conventional encryption are already pretty secure. But if the NSA wants to check your conversation, I bet it can. With quantum cryptography, this is a different story.
Quantum cryptography promises to stop such eavesdroppers. The system works by first establishing a 'key' that provides instructions on how to decode an incoming message. This key is built into the quantum state of photons. Intercepting a message breaks the key and alerts the sender and intended recipient to the security breach, because the very act of observing a quantum state changes it.
The Quantum Information Group at Toshiba gives more details on this subject on this page about Security from Eavesdropping. Below is a diagram illustrating the concept (Credit: Toshiba's Cambridge Research Laboratory).
Using single photons to carry the bit material for the key prevents undetected eavesdropping. 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, as shown in the illustration. Single photons do not split, so if the hacker (Eve) measures the photons on the fibre, they will not reach the intended recipient (Bob). Only the photons that arrive at Bob are used to form the key, so Eve cannot gain any useful information by this crude 'tapping' attack.
The first commercial applications of quantum cryptography are now about one year old. However, this new system offers new levels of performances, according to Nature.
Unlike previous systems, which become unreliable when they heat up, this device can run continuously for more than four weeks, says Shields. The quantum information can only go so far before being corrupted by random interactions with surrounding material, however. "We've shown this can work over 120 kilometres of fibre," says Shields.
Toshiba has already built a Quantum Cryptography Prototype. And the research work has been published by Applied Physics Letters (Vol. 84, Issue 19, Pages 3762-3864, May 10, 2004) under the title "Quantum key distribution over 122 km of standard telecom fiber." Here is a link to the abstract.
We report a demonstration of quantum key distribution over a standard telecom fiber exceeding 100 km in length. Through careful optimization of the interferometer and single photon detector, we achieve a quantum bit error ratio of 8.9% for a 122 km link, allowing a secure shared key to be formed after error correction and privacy amplification. Key formation rates of up to 1.9 kbit/s are achieved depending upon fiber length. We discuss the factors limiting the maximum fiber length in quantum cryptography.
Finally, here is a link to the full paper (PDF format, 14 pages, 68 KB).
Sources: Mark Peplow, Nature, April 28, 2005; Toshiba's Cambridge Research Laboratory website
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