NIST doing crypto key exchanges at the speed of light

The National Institute of Standards and Technology is pushing the speed limit on cryptographic key exchanges on its new quantum communications test bed.

The May 3 issue of Optics Express, the online journal of the Optical Society of America, described a demonstration of NIST's quantum key distribution system that delivered usable bits in the form of individual photons at the rate of 1Mbps.

'We have cleared 3.5Mbps within the current parameters,' said Joshua C. Bienfang, a physicist in the Electron and Optical Physics Division.

NIST is not the first organization to use quantum physics to exchange keys for encryption. At least two companies, MagiQ Technologies Inc. of New York and the Swiss Company id Quantique, have commercial products using the technology. But NIST is the fastest, by a factor of 100.

'Our goal is to see how fast we can do quantum key distribution,' Bienfang said.

The process involves sending individual photons'elemental particles of light'in different polarizations and orientations to represent individual bits. The laws of physics declare that observing an elemental particle such as a photon changes it, making eavesdropping essentially impossible.

'Detecting a photon involves its destruction,' said Charles Clark, chief of the Electron and Optical Physics division. 'If someone tried to eavesdrop, they would induce an error rate that would be so high it would be noticed.'

The system does not encrypt data; it only exchanges bits that can be used for an encryption key.

'This is not a matter of sending information, but of generating a bunch of random bits' and delivering them securely, Clark said.

Work on the test bed, which uses a line-of-sight optical link between two buildings on the NIST campus in Gaithersburg, Md., began about two years ago and the system began functioning about two months ago. There is a lot of work yet to be done on photon generation and detection, but the hardware already has outstripped the software components, Bienfang said.

'This has exceeded the ability to do error correction,' he said.

A separate team is working on that problem.

About the Author

William Jackson is a Maryland-based freelance writer.

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