Opacity and Structural Resilience in Cyber-Physical Systems

This poster surveys results obtained by the project team in the general area of cybersecurity for Cyberphysical Systems (CPSs). In particular, the team has shown how the notion of opacity, which has been defined and studied in the context of discrete-event systems, may be lifted to linear time-invariant and switched systems. Opacity is concerned with the ability of a system to conceal aspects of its behavior ("secrets") from a passive adversary who can observe aspects of system dynamics. The obtained results show in the case of a single adversary, opacity for linear-time invariant (LTI) systems is reducible to so-called output controllability, and that in the case of multiple adversaries and switched linear systems, reasonable notions of opacity can be characterized as state-reachability problems. Other work concerns the resilience of LTI systems, represented structurally, to denial of service attacks. The poster describes how these questions can be answered automatically using graph-theoretic algorithms that run in polynomial time.