NEC, Mitsubishi link quantum encryption networks

New method marks important step on the road to commercial use of quantum cryptography

NEC and Mitsubishi Electric have developed a method that allows their quantum encryption systems to work together, an important development on the road to the commercial use of quantum cryptography, the companies said Friday.

It is the first time in Japan, and probably the world, that such interoperability has been accomplished, the companies said. The University of Tokyo also contributed to the effort.

Quantum cryptography systems are being developed to form the base of future ultra-secure communications systems. They are used to exchange an encryption key between two users who then use the key to encrypt data on a conventional network. The keys are encoded onto particles of light called photons. As photons cannot be split, they can only end up in one place, either with the intended receiver or with an eavesdropper. If a complete key is received, it can be trusted with the knowledge that no eavesdropping has taken place en route.

Several companies and government-backed research labs are developing such systems, but there is no standard so they do not yet work together. Using the method outlined by the three research partners on Friday, interoperability is possible.

It's based around a single PC that sits at a secure center, said Mitsuru Matsui, a senior manager with Mitsubishi Electric's information security technology department, at a Tokyo news conference.

The PC is connected via a standard Ethernet connection to quantum encryption boxes from NEC and Mitsubishi. A single key is issued by the PC to each box, both of which are connected via a fiber optic link to companion boxes at distant locations. A quantum cryptography link enables the key to be sent securely from the center to the distant locations, said Matsui.

With the key distributed, users in the distant locations can exchange data with each other across a conventional network with confidence that the key hasn't been compromised. This is possible even though each user has a quantum system from a different vendor, he said.

In addition to allowing users of incompatible quantum cryptography systems to work together the system has an additional benefit, said Matsui. Current systems are limited to a distance of about 100 kilometers but with the center sitting between two networks the communications distance is effectively doubled.

Both companies hope to produce a commercial system based on the technology outlined Friday in about five years, they said. Quantum cryptography systems themselves are being eyed by governments and organizations such as banks for their high security as a replacement for current encryption technologies.

The system was developed as part of a quantum encryption technology project sponsored by Japan's National Institute of Information and Communication (NICT) that ran for four years and ended last year.

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