The relationships between safety and security

Safety and security have long been considered as independent issues, and dealt with by separated communities. In fact, they share substantial commonalities that have already supported several reciprocal inspirations on methodological, technological or architectural aspects. Nevertheless, the exchanges between the associated communities are still very limited and the potential for cross-fertilization is still significant. Moreover, the convergence of safety and security requirements and measures on the same systems is a recent phenomenon with consequences which are still to be mastered. This thesis deals with the relationships between safety and security covering both the cross-fertilization on a methodological point of view and the consequences of their convergence. It has led to three main contributions: - The SEMA referential framework, which helps to make the latent differences underlying the use of the terms 'security' and 'safety' explicit by a simple graphical notation; - The adaptation of the BDMP formalism from the safety area to security, providing an attractive trade-off between readability and modeling power in attack modeling; - A new approach, based on BDMP, enabling graphical representation, qualitative and quantitative analysis of situations combining safety and security risks. For each contribution, several possible enhancements and alternatives have been identified, which will make sense as the safety and the security communities strengthen their links. Beyond the contributions, this Ph.D. thesis aims at being both a manifestation and an invitation for such a rapprochement. (author)