Determination of Security Index for Linear Cyber-Physical Systems Subject to Malicious Cyber Attacks

Abstract

In this paper, we are mainly concerned with formulation and computation of security indices for linear cyber-physical systems (CPS), where both input and output channels are subjected to malicious cyber attacks. The approaches in the literature for computing security indices (and consequently vulnerability analysis) of CPS are based on algebraic methods and system matrices. In this paper, for the first time in the literature we formally address the security index computation from a geometric systems theory perspective. By utilizing this framework we provide a methodology for computing an upper bound on the security index in a quadratic time complexity with respect to the order of the system (i.e., O(n)). This represents an improvement when compared with the currently available approaches in the literature that have polynomial time complexity (i.e., O(n3) or higher). Unlike the approaches in the literature our methodology does not impose any restriction on representation of the system. A numerical example is also provided to demonstrate and illustrate the capabilities of our proposed approach.