Biblio

In this paper, System Theoretic Process Analysis (STPA) method was used to analyze the security of Temporary Speed Restriction (TSR) sending scenario in train control system based on vehicle-vehicle communication. The security of this scenario was analyzed according to the analysis process of STPA method. Firstly, Unsafe Control Actions (UCAs) in this scenario were identified and Control Defects (CDs) were analyzed. After that, the corresponding Security Design Requirements (SDRs) were formulated according to the obtained control defects. Finally, the time automata network model of TSR sending scenario was established to verify SDRs. The result shows that: STPA method is suitable to discover the unsafe factors and safety hazards of train control system and take corresponding safety measures to prevent the occurrence of accidents.

Agile methodologies are becoming widespread in modern software development. However, due to a lack of safety assurance activities, agile methods are criticized for being inadequate for the development of safe software. Safety analysis and safety verification are complementary methods for safety assurance. Yet, both usually rely on traditional, waterfall-like processes. Therefore, it is strongly needed to integrate an appropriate safety analysis approach into agile software development processes driving architecture design and verify the safe design at the code level. This paper presents a novel agile process model "S-Scrum" based on the existing development process "Safe Scrum" and extended by a safety analysis method and a safety verification approach based on STPA (System-Theoretic Process Analysis). The proposed agile development process S-Scrum can be separated into three parts: (1) performing safety-guided design by STPA inside each sprint. (2) Verifying safety requirements at the code level by using model checking. (3) Replacing traditional RAMS (Reliability, Availability, Maintainability, Safety) validation on the final product by STPA safety analysis. We adopt other aspects from the original Safe Scrum. Finally, the feasibility of S-Scrum is illustrated with the example of an airbag system.