A novel secure observer-based controller and attack detection scheme for Networked Control Systems

This paper proposes security techniques for detecting and counteracting attacks in Networked Control Systems (NCSs). A partially homomorphic based encryption technique, namely the Paillier scheme, is used to protect the confidentiality of the transmitted data over the network against eavesdropping attacks. An integrated secure and private observer-based controller with guaranteed stability together with a secure and private observer-based detection system has been developed. We start with an encrypted observer. Then, an observer-based encrypted controller is added to stabilize the system. Besides, an encrypted observer-based detection algorithm has been used to detect false data injection attacks. Moreover, in our design, the computations on the observer, the controller, and the decision-maker operate on encrypted data while protecting against eavesdropping attacks. Using digital processors in cyber systems leads to quantized transmitted signals through the network and also to design the observer and controller operations in such a way that they work on quantized data efficiently. Limitations on the parameters of the quantizations and the encryption scheme are given to ensure the stability of the closed-loop system and guarantee reliable bounds on the closed-loop performance. Simulation results using Tennessee Eastman Process demonstrate the effectiveness of the proposed scheme.