Safety And Security Integrated Sil Evaluation Using The Nfr Approach

The paper addresses the issue of evaluating Safety Integrity Levels (SIL) from the perspective of concerns related jointly to safety and security. We apply the Non-Functional Requirements (NFR) approach, which relies on evaluation of both safety and security at the architectural level. Used in two case studies on industrial automation systems, the results show that the method yields reasonable results, no weaker than other methods of SIL evaluation, such as risk graphs, and can be used for both SIL determination and verification.