A Framework for Evaluating Security in the Presence of Signal Injection Attacks
This work addresses security vulnerabilities in sensor-based systems across critical applications like medical devices and nuclear plants, providing a foundational framework for evaluation.
The authors tackled the lack of a unifying framework for evaluating security against signal injection attacks on sensors, introducing a system and threat model, security definitions, and an algorithm for calculating security levels, applied to smartphone microphones and commercial ADCs with practical measurements.
Sensors are embedded in security-critical applications from medical devices to nuclear power plants, but their outputs can be spoofed through electromagnetic and other types of signals transmitted by attackers at a distance. To address the lack of a unifying framework for evaluating the effects of such transmissions, we introduce a system and threat model for signal injection attacks. We further define the concepts of existential, selective, and universal security, which address attacker goals from mere disruptions of the sensor readings to precise waveform injections. Moreover, we introduce an algorithm which allows circuit designers to concretely calculate the security level of real systems. Finally, we apply our definitions and algorithm in practice using measurements of injections against a smartphone microphone, and analyze the demodulation characteristics of commercial Analog-to-Digital Converters (ADCs). Overall, our work highlights the importance of evaluating the susceptibility of systems against signal injection attacks, and introduces both the terminology and the methodology to do so.