A Six-Step Model for Safety and Security Analysis of Cyber-Physical Systems

A Six-Step Model (SSM) is proposed for modeling and analysis of Cyber-Physical System (CPS) safety and security. SSM incorporates six dimensions (hierarchies) of a CPS, namely, functions, structure, failures, safety countermeasures, cyber-attacks, and security countermeasures. The inter-dependencies between these dimensions are defined using a set of relationship matrices. SSM enables comprehensive analysis of CPS safety and security, as it uses system functions and structure as a knowledge-base for understanding what effect the failures, cyber-attacks, and selected safety and security countermeasures might have on the system. A water treatment system is used as an example to illustrate how the proposed model could serve as a useful tool in the safety and security modeling and analysis of critical infrastructures.