Conflict Analysis and Resolution of Safety and Security Boundary Conditions for Industrial Control Systems

Safety and security are the two most important properties of industrial control systems (ICS), and their integration is necessary to ensure that safety goals do not undermine security goals and vice versa. Sometimes, safety and security co-engineering leads to conflicting requirements or violations capable of impacting the normal behavior of the system. Identification, analysis, and resolution of conflicts arising from safety and security co-engineering is a major challenge, an under-researched area in safety-critical systems(ICS). This paper presents an STPA-SafeSec-CDCL approach that addresses the challenge. Our proposed methodology combines the STPA-SafeSec approach for safety and security analysis and the Conflict-Driven Clause Learning (CDCL) approach for the identification, analysis, and resolution of conflicts where conflicting constraints are encoded in satisfiability (SAT) problems. We apply our framework to the Tennessee Eastman Plant process model, a chemical process model developed specifically for the study of industrial control processes, to demonstrate how to use the proposed method. Our methodology goes beyond the requirement analysis phase and can be applied to the early stages of system design and development to increase system reliability, robustness, and resilience.