A Model-based Approach to Interdependency between Safety and Security in ICS

Wide use of modern ICT technologies brings not only communication efficiency, but also security vulnerabilities into industrial control systems. Traditional physically-isolated systems are now required to take cyber security into consideration, which might also lead to system failures. However, integrating security and safety analysis has always been a challenging issue and the various interdependencies between them make it even more difficult, because they might mutually enhance, or undermine. The paper proposes an integrating framework to (i) formalise the desired and undesired properties to be safe(unsafe) or secure(insecure), including the dependencies between them, (ii) evaluate if a query state reaches a safe(unsafe) or secure(insecure) state, and further quantify how safe or secure the state is. In this way, we can accurately capture the benign and harmful relations between safety and security, particularly detecting and measuring conflicting impacts on them. Finally, this framework is implemented by answer set programming to enable automatic evaluation, which is demonstrated by a case study on pipeline transportation.