Tapping Underwater Wireless Optical Communication in Pure Water and Natural Dead-Sea Ultra-high-salinity Water by Diffraction Grating

Although underwater wireless optical communication (UWOC) receives much interest lately, security issues associated with it get little attention. In this paper, we show how a message communicated using UWOC can be eavesdropped without a sender's or addressee's awareness, by employing a diffraction grating. We also analyze the propagation of multiple diffracted Gaussian beams in water, and show for the first time that UWOC is feasible even in natural ultra-salty water taken from the Dead-Sea. We evaluate how far from the addressee the message could be eavesdropped, and discuss different possibilities of tapping the channel - one from the air and one underwater.