Encrypted Control System with Quantizer

This paper considers the design of encrypted control systems to secure data privacy when the control systems operate over a network. In particular, we propose to combine Paillier cryptosystem with a quantizer whose sensitivity changes with the evolution of the system. This allows the encrypted control system to balance between the cipher strength and processing time. Such an ability is essential for control systems that are expected to run real-time. It also allows the closed-loop system to achieve the asymptotic stability for linear systems. Extensions to event-triggered control and nonlinear control systems are also discussed.