Time-Stamp Attacks on Remote State Estimation in Cyber-Physical Systems

In this article, we consider the security of remote state estimation in cyber-physical systems (CPS), where a wireless sensor sends the measurement of the considered system to a remote state estimator using a wireless channel. In this scenario, time-stamp technology is commonly used to record the time characteristic of the data for different objectives, such as realizing time synchronization and dealing with time delays. We consider a potential threat to this mechanism, and investigate a time-stamp attack, where a malicious adversary manipulates data packets to degrade the estimation performance of the remote estimator. In particular, we assume that the attacker can alter the time-stamps of any two packets. We consider two types of sensor transmission - namely, innovation and local estimation, respectively, and analyze the evolution of the remote estimation error covariance for both cases. Furthermore, we characterize the optimal attack strategy that maximizes the estimation error covariance from the attacker's point of view. Finally, we present numerical simulations to demonstrate the effectiveness of our results.