Researchers claim stealth encryption breakthrough

Two US researchers believe they have found a way to transmit information safely over an optical network without fear of interception. The technique hinges on transmission of encrypted data in the "noise" of signals along fibre-optic cables.

Their method take advantage of the fact fibre-optic systems inevitably have low levels of "noise" — the random jitters in the light waves that are used to transmit information through a network. The technique, developed by two researchers at Princeton University, hides the secret encrypted message in this optical noise.

The sender first converts the secret message into a short pulse of light. Commercially available Code Division Multiple Access (CDMA) equipment spreads the intense, short pulse into a long, faint stream of optical data. The breakthrough comes from the ability to make the signal fainter than the noisy jitters in the fibre-optic cable.

The intended recipient decodes the message by using information about how the secret message was originally spread out, using another optical device to change the message back to its original state. The method should be secure because even if eavesdroppers knew a secret transmission was taking place, any slight imperfection in their knowledge of how the secret signal was spread out would make it too hard to pick out amid the more intense public signal.

The technique was developed by researchers Wu and Evgenii Narimanov of Princeton University and was presented this week at the annual meeting of the Optical Society of America: traditionally a showcase for new ideas. The paper was published originally on 1 May.