Dynamic Watermarking for Cyber-Security of Nonlinear Stochastic Systems
Tzu-Hsiang Lin, P. R. Kumar · 2024
As cyber-physical systems form the core of many critical infrastructures, ensuring their safety is essential. The sensor measurements of networked cyber-physical systems can potentially be compromised, resulting in the misbehavior of the overall system. Indeed there have been a number of such attacks. Dynamic Watermarking is a proactive method whose goal is to detect such cyber attacks. It superimposes a small secret stochastic excitation onto signals in the system, such as control inputs of actuators or sensor measurements. Based on an examination of the signals purportedly returned, for example, by the sensors, it determines if the measurements have been tampered with. Previous theory for detection guarantees provided by Dynamic Watermarking has been restricted to linear stochastic systems. This paper examines the Dynamic Watermarking method for nonlinear stochastic systems. We show that Dynamic Watermarking for detecting attacks can be extended to certain systems in backstepping form. We present the analytical proofs, as well as simulation results.