NEC delays quantum cryptography system

NEC has delayed the introduction of its first quantum cryptography system by three to four years due to performance and cost issues, the company said Tuesday.

NEC had originally planned to start selling the system later this year, but recent tests showed that its technology is still years from being ready for commercial use, it said.

Quantum cryptography is supposed to improve the security of data communications because when users exchange cryptographic keys they can tell whether or not the key has been tampered with during transmission. The systems work by encoding each bit of the encryption key on individual photons by setting their polarization. As photons cannot be split, and are destroyed when their polarization is measured, they can only end up in one place, either with the receiver or with an eavesdropper.

Such systems are difficult to build. Common problems include generating sufficient photons for sufficient periods of time to allow for a fast and steady stream of data, and ensuring that enough of the photons pass through long fiber optic cables without getting scattered and lost. Other companies including Fujitsu Ltd. are also developing quantum cryptography systems.

NEC demonstrated a system last September that it said generated quantum keys at 100K bps (bits per second) and could transmit them over distances up to 40 kilometers. Such performance should have been good enough to commercialize the technology in the second half of this year, it said at the time.

However, keys generated by that system contained errors, and the system was not tested on commercial fiber optic networks, with many junctions and other properties that disperse the streams of photons, Diane Foley, an NEC spokeswoman, said on Tuesday.

NEC developed a newer system with improvements including software to strip out the errors. It was tested recently over a 16.3 km commercial fiber optic cable used by a local network company and worked at just over 13K bps. The error rate was greatly improved, but the data rate achieved over the shorter distance was not sufficient for the technology to be offered commercially, Foley said.

NEC now estimates that it will take three to four years to make the technology good enough for commercial use. It also needs to lower the costs of the equipment used, she said, without giving details.

She declined to say what data rate the company considers appropriate for commercial use, but such systems would need to work over at least 40 kilometers, she said.

"This has brought [NEC] extremely close to a commercial system. The next steps are to verify higher speeds over longer distances," she said.