A Process-Oriented and Coalescent Analysis Method for Safety and Security in Railway Systems

The convergence of network, electronic, and control technologies has expanded the attack surface of industrial control systems (ICSs), necessitating the integration of functional safety and cybersecurity. Existing methods often treat safety and security as isolated domains, overlooking their interdependence in modern ICSs. This article proposes a novel methodology, Process-Oriented and Coalescent Analysis (POCA), to bridge this gap through an integrated safety and security analysis. Unlike previous approaches, POCA focuses on the intersection of cyberthreats and functional interactions, offering a new perspective on threat modeling. Applied to a railway signal system, a representative ICS that has received insufficient attention in cybersecurity research, POCA incorporates cyberattack scenarios, system service processes, and safety constraints to identify and assess risks. The analysis results highlight POCA’s effectiveness in uncovering vulnerabilities at the intersection of functional safety and cybersecurity, providing actionable insights for system design and operation.