Eavesdropping and jamming are a growing danger to optical communications systems, which transmit a rapidly growing amount of digital data that require a high level of security.Now, engineers at Ben-Gurion University of the Negev in Beersheba and Bar-Ilan University in Ramat Gan have developed an encryption technique that enables stealthy transmission of any optical communications signal by spreading it below the “noise” level (the level of electromagnetic interference) in both time and frequency domains (spectrums).As a result, a would-be eavesdropper who tries to intercept the transmitted signal only detects noise, because the signal is hidden below the noise level. This means that only authorized users who know the authorized pattern can detect and decipher the signal (“spreading key”).Prof. Dan Sadot of BGU’s department of electrical and computer engineering, working with Prof. Zeev Zalevsky, head of the electrooptics study program at Bar-Ilan’s engineering faculty with doctoral student Tomer Yeminy, developed the novel concept for stealthy fiber optical communications.The researchers have prepared a simulation that could be used to build a prototype, and the method is in the midst of being patented.“It is analogous to many soft sounds of a lovely symphony scattered through a recording of background noise,” the researchers said. “The authorized user who knows the ‘spreading key’ is the only one able to detect and enjoy the symphony without the noisy background. It should be noted that analysis shows that it will take about [10 to the 24th power – a septillion, or 1,000,000,000,000,000,000,00 0,000] years for an eavesdropper to break the encryption key, which means that eavesdropping is very hard. This method could also be useful in improving the immunity of the fiber optic communications system to jamming,” say the researchers.“Continuing the above analogy, it is equivalent to talking at the same time as a person speaking loudly. Concealment depends on how loudly the other person talks and, moreover, the quality of both conversations will degrade,” they argue.