Watermark-Based Proactive Defense Strategy Design for Cyber-Physical Systems With Unknown-but-Bounded Noises

In this article, a novel proactive attack defense strategy is proposed to deal with the secure remote estimation issue in cyber-physical systems with unknown-but-bounded noises in the presence of man-in-the-middle attacks. It is assumed that the residue calculated by the smart sensor is sent to the remote estimator and the abnormal intrusion detector via a wireless network, and the watermark is assumed to belong to a zonotope. In order to guarantee the detection rate, the data processes and the watermark are time-varying and secret to an adversary. Moreover, the effect on system performance caused by the watermark can be removed when the system is attack free. Furthermore, four different attack scenarios are discussed to analyze the detection ability of the proposed defense approach, and the designed strategy can be applied to detect replay attacks. Finally, an unmanned aircraft system subject to malicious attacks is leveraged to illustrate the effectiveness of the proposed proactive defense strategy.