Good Vibes: A PWM-Enabled Covert Channel for Securing UAVs Operations

This paper proposes an innovative vibration-based communication system on a wireless medium for Unmanned Aerial Vehicles (UAVs), in which a covert channel is established by relying on the inherent characteristics of vibration signatures generated by the motors and propellers mounted on the UAV. Different vibration patterns, generated by purposely varying the Pulse Width Modulation (PWM) signals driving the UAV motors according to a predefined scheme, can be remotely detected by measurements performed with a radar sensor deployed at, for instance, a Critical Infrastructure (CI) to be safeguarded. The system analyses the vibrational patterns, via frequency and displacement measurements exploiting a Discrete Fourier Transform (DFT) approach, to decode information symbols on a constellation diagram. As a result, a localised channel is created. The latter is also inherently secure against attacks like jamming and spoofing, typical of traditional Radio Frequency (RF) communications. Experimental results validate the feasibility of the proposal, by identifying four encoded symbols that can be potentially exploited to set up a communication protocol.