The IEMI Effect: On the Efficacy of PCB-level Countermeasures in Adversarial Environments

Sensing data integrity in a cyber-physical system (CPS) is critical to its safe operation. Intolerable data manipulation can potentially lead to very hazardous consequences. Numerous countermeasures have proven capable of protecting sensitive circuitry, cabling, and their signals from the effects of electromagnetic interference (EMI). However, in the case of intentional electromagnetic interference (IEMI), existing countermeasures possess limited efficacy. IEMI-capable adversaries attack the signal processing circuits and signal paths between sensors/actuators and the controller, seeking to manipulate the signals and falsify data. On a printed circuit board (PCB), the traces carrying these signals act as unintentional receiving antennae to a time-varying electromagnetic field generated by an adversary. In this paper, we demonstrate IEMI attacks on the PCBs used in electric vehicle (EV) charging systems, a highly safety-critical CPS. To mitigate these attacks, we implement passive PCB-level countermeasures, namely, differential signaling, via-fencing, and optical fiber for interconnects. In addition, we propose and implement a multiplexer-based defense that dynamically modifies the route path and evades the adversary. All four countermeasures have been extensively evaluated against multiple adversarial setups and ranked based on their impact. Further, adaptive attacker strategies have been proposed to circumvent the effective countermeasures.