University of Massachusetts at Amherst researchers say they have developed a method to camouflage messages in a way that is mathematically guaranteed. They also have developed a proof-of-principle demonstration for the new method.
"We have built the first operational system that provides mathematically proven covert communication over a physical channel," the researchers say.
The technique relies on a method of communication called pulse position modulation, which divides each second into a number of time bands that each correspond to a symbol. The system requires that the sender and receiver agree on the band structure and the symbols they refer to, all of which must be done in advance of the message being sent.
The researchers focused on calculating the number of signaling photons that can be sent in a noisy environment while guaranteeing that an eavesdropper cannot distinguish them from the background. This is possible because the eavesdropper does not know when the signaling pulses are sent and always detects additional noisy photons that further hides the message.
The researchers say they proved the message can always be camouflaged with an arbitrary probability of detection, provided noise is within certain limits. "We demonstrated that provably covert optical communication is practically achievable," they say.
From Technology Review
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