Secret-Key Based Non-Coherent Signalling to Mitigate Reactive Injection Attacks

When communicating under strong adversarial models, non-coherent signalling schemes are known to be robust when compared to their coherent counterparts. In this regime, we consider a reactive adversarial model wherein the adversary listens to the ON-OFF keying based signalling from the victim and then injects energy on the victim’s frequency only when it detects the OFF-state of the transmitter. We show that this attack model forces the receiver to witness non-zero energy levels on all the time-instants thereby degrading the error performance. To circumvent this problem, we propose a secret-key based non-coherent signalling wherein the transmitter and the receiver use a pre-shared key to pick a random energy level from a dictionary when communicating the ON-state. As a result, the adversary, will not be able to inject the appropriate energy level with probability one. For the proposed countermeasure, first we study its uncoded variant, and propose an optimization problem over the choice of the non-zero energy levels in the dictionary in order to minimize the average error-rate for the victim. Subsequently, we also propose a coded non-coherent signalling scheme, and study the choice of decoding strategies to further improve the average error over the uncoded counterpart. Through extensive simulations, we show that the proposed countermeasure assists the victim in achieving high reliability communication with nonzero rate despite the presence of a reactive adversary.