Enhancing CHASSIS: A Method for Combining Safety and Security

Safety and security assessments aim to keep harm away from systems. Although they consider different causes of harm, the mitigations suggested by the assessments are often interrelated and affect each other, either by strengthening or weakening the other. Considering the relations and effects, a combined process for safety and security could save resources. It also improves the reliability of the system development when compared to having two independent processes whose results might contradict. This paper extends our previous research on a combined method for security and safety assessment, named CHASSIS, by detailing the process in a broader context of system development with the help of feedback from a safety expert. The enhanced CHASSIS method is discussed based on a case from the Air Traffic Management domain.