SoK: A Minimalist Approach to Formalizing Analog Sensor Security

Over the last six years, several papers demonstrated how intentional analog interference based on acoustics, RF, lasers, and other physical modalities could induce faults, influence, or even control the output of sensors. Damage to the availability and integrity of sensor output carries significant risks to safety-critical systems that make automated decisions based on trusted sensor measurement. Established signal processing models use transfer functions to express reliability and dependability characteristics of sensors, but existing models do not provide a deliberate way to express and capture security properties meaningfully.Our work begins to fill this gap by systematizing knowledge of analog attacks against sensor circuitry and defenses. Our primary contribution is a simple sensor security model such that sensor engineers can better express analog security properties of sensor circuitry without needing to learn significantly new notation. Our model introduces transfer functions and a vector of adversarial noise to represent adversarial capabilities at each stage of a sensor's signal conditioning chain. The primary goals of the systematization are (1) to enable more meaningful quantification of risk for the design and evaluation of past and future sensors, (2) to better predict new attack vectors, and (3) to establish defensive design patterns that make sensors more resistant to analog attacks.