Safer signals over optic networks

A new technique could allow inexpensive, widespread, and secure transmission of confidential and sensitive data by governments and businesses over existing optical fibre networks.

Bernard Wu and Evgenii Narimanov of Princeton University developed the method for transmitting secret messages over existing public optic-optic networks, such as those operated by Internet service providers.

Unlike standard encryption, in which computer software scrambles a message, it uses the physical properties of an optical-fibre network to cloak a message. The sender transmits an optical signal that is so faint that it is very hard to detect, let alone decode.

The method takes advantage of the fact that optics-optics systems inevitably have low levels of "noise," random jitters in the light waves that transmit information through the network. The new technique hides the secret message in this optical noise.

The sender first translates the secret message into an ultra-short pulse of light. Then, a commercially available optical device called an optical CDMA encoder spreads the intense, short pulse into a long, faint stream of optical data, so that the optical message is fainter than the noisy jitters in the optic-optic network. The intended recipient decodes the message by employing information on how the secret message was originally spread out and using an optical device to compress the message back to its original state. The method is very secure; 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 amidst the more intense public signal.