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Senior Editor, Network World

Quantum crypto coming to light

Apr 19, 20045 mins

Quantum cryptography, a technology that uses photons to encrypt communications over fiber-optic lines and the air, is starting to come out of the laboratory and into commercial use.

MagiQ Technologies recently began selling the world’s first commercially available point-to-point quantum-crypto box. Separately, a Swiss company called Id Quantique will start pilot tests of its encryptor with banks and other businesses. Both companies’ boxes start at $50,000.

“We are confident there will be a market, but the question is: How long will it take to grow?” says Grigoire Ribordy, founder of Id Quantique.

The technology has been in the works for two decades and has received considerable financial backing from the U.S. military. Supporters say quantum cryptography will make cracking datastreams more difficult than ever, in part because it makes possible the changing of encryption keys – such as those based on Triple-DES or Advanced Encryption Standard – at the dizzying speed of about 100 times per second. This so-called quantum-key distribution method is potentially a better way to exchange keys for point-to-point encryption than what is offered in current symmetric-key technologies. Quantum crypto also automatically detects when anyone is trying to eavesdrop on a communications stream.

“With quantum key distribution there’s no way of breaking the key,” says Charles Bennett, IBM research staff member and IBM fellow. He invented the basic quantum crypto technology, called BB84, with colleague Gilles Brassard of the University of Montreal, back in 1984. “It differs from the more ordinary methods, such as Diffie-Hellman Factoring.”

Despite such advances, the technology has its challenges, including distance limitations.

Id Quantique’s encryption/decryption unit, dubbed the ID500 (it features optical phase modulators, couplers, single-photon detectors and diodes), is limited to less than 62 miles before the photons performing the encryption lose their force over a fiber-optic line. “For the first pilot tests, we’ll only go a few kilometers,” Ribordy says.

MagiQ’s QPN gateway also has distance issues, which the company tackles by adding a repeater after 74 miles “to regenerate the photon amplification,” says Andrew Hand, vice president of business development. The box is limited to encryption at 100M bit/sec, although the company hopes to push that to 10G bit/sec.

There are no commercial wireless “free space” quantum crypto products yet, but many research labs are seeking to push back the barriers there as well. The National Institute of Standards Technology has attained a distance of 18 miles at 312M bit/sec with its experimental equipment, says research scientist Carl Williams.

Quantum crypto, however, has failed to win over some experts of traditional crypto methods, who argue that the technology is overkill for most businesses, which already have many tried-and-true, strong, point-to-point encryptors in place.

“It’s technically intriguing, it offers higher strength and speed potentially, but do we have applications that need that?” says Taher Elgamal, founder of company Securify and the inventor of the widely used Secure Sockets Layer protocol for the Web.

“I don’t think it provides anything in terms of practical advances,” says crypto expert Bruce Schneier, founder of security firm Counterpane. “I don’t think it’s anything more than a fascinating quantum mechanics area of research.”

The U.S. government, in particular the military, begs to differ. It has long seen the potential of free-space quantum crypto in securing satellites, for example. Quantum crypto was also on the agenda at last week’s International Society for Optical Engineering’s Defense and Security Symposium in Orlando.

Three years ago, the Defense Advanced Research Projects Agency (DARPA) started the Quantum Information Science and Technology program, and millions of dollars in research funding related to quantum cryptography has since gone to universities and companies to show it can work.

BBN Technologies, for instance, is doing DARPA-funded research in both free space and fiber-optics quantum crypto.

“Every year DARPA wants to see some breakthroughs,” says Henry Yeh, program director for quantum cryptography at BBN. “The long-term goals are things like earth-to-space communications and ground use.”

BBN’s lab is working on a prototype for satellite communications, and Chip Elliott, a senior engineer at BBN, says he’s convinced it’s going to be possible to eventually get much better mileage over the air than in fiber.

“With fiber, you can only get about 50 miles due to single photons getting absorbed by the fibers,” he says. “But space-based, it looks like you could get 10,000 miles.” The air brings its own problems, though, with clouds, dust and unsettled conditions creating interference.

BBN, which has so far only used its quantum-cryptography gear in the lab, plans its first outside tests next month by setting up dark-fiber links with Harvard University to encrypt data between the two sites. “The step after that would be to try it on normal installed telecom fiber,” Elliott says.

Some technology watchers say quantum crypto continues to have an aura of secrecy because the greatest demand for it is coming from the military and financial sectors that guard very sensitive data. “If you need it, you don’t want people to know,” says Trent Henry, an analyst at Burton Group.