Switching for Unpredictability: A Proactive Defense Control Approach

In this paper, we consider the problem of securely operating a cyber-physical system in an adversarial environment. The defending mechanism we introduce is proactive in nature and employs the principles of moving target defense. The defense implementation utilizes a switching structure to persistently and stochastically alter the behavior of the system with respect to both its actuators and its sensors. Thus, the ability of an adversary to successfully scan the system in preparation for the attack is decreased. The unpredictability of the system's operation is quantified by an entropy metric which is subsequently optimized. Theorems are presented that show stability of the system under proactive switching. Simulations show the efficacy of the proposed approach on a simplified aircraft model.