Across the Interface: Eavesdropping on Underwater Communications in Air

Abstract

This paper examines the problem of wireless eavesdropping on communications where the victim and eavesdropper both reside adjacent but in entirely separate mediums. An example of this kind of environment is found in air and water. Our work aims to develop a scalable method to eavesdrop across the air-water interface. So far, wireless system designers and experts alike have assumed that eavesdropping on communication from outside of the medium is practically impossible and therefore, the air-water interface offers a natural safety mechanism that protects communications from leaking outside to adjacent mediums.

This paper plans to dispute this cross-medium security claim and instead proposes a wireless eavesdropping exploit called 'micro-doppler underwater terrestrial eavesdropping' (MUTE) that is the plans on allowing an airborne node such as a drone to be capable of non-coherently eavesdropping on ongoing underwater communications. MUTE similar to prior works in the air-water communication domain in that it takes advantage of the fact devices submerged in water rely on acoustic communication. The acoustic communication causes micrometer displacements of the water's surface as pressure waves collide and reflect off the the air-water interface. MUTE is able to decode underwater communications by measuring the micrometer displacement of the water's surface using a radar.

In this paper, validate the MUTE via simulation using synthetic data generated from real underwater communication as well as build a working prototype that supports live underwater communication. We evaluate the performance of our underwater communication chain within a water tank and discuss methods by which underwater communication can be improved as well as next steps in testing the an end-to-end MUTE exploit.