Controlled Mode Distinguishability for Cybersecurity

Cyber-physical systems (CPSs) are a class of systems integrating cyber and physical components, and their security issues have gained a lot of attention in recent years. CPSs are modeled as hybrid systems in this letter since the logical and physical behaviors of CPS can be mapped to the discrete-state and continuous-state dynamics of the hybrid system, respectively. Motivated by the importance of situation awareness in an adversarial environment, we consider the mode distinguishability problem for a class of hybrid systems that can describe compromised CPSs. It is found that even though some modes of the hybrid system may not be distinguishable without knowing the attack inputs, the modes could be controlled distinguishable, which means their behaviors can be differentiated under certain control inputs. In this letter, the characterization of controlled distinguishability is studied, and the problem of finding control inputs for mode identification is proposed.