Latest technological trends lead towards systems connected to public networks even in critical domains. Bringing together safety and security work is becoming imperative, as a connected safety-critical system is not safe if it is not secure. The main objective of this study is to investigate the current status of safety and security co-analysis in system engineering by conducting a Systematic Literature Review. The steps of the review are the following: the research questions identification; agreement upon a search string; applying the search string to chosen databases; a selection criterion formulation for the relevant publications filtering; selected papers categorization and analysis. We focused on the early system development stages and identified 33 relevant publications categorized as: combined safety and security approaches that consider the mutual influence of safety and security; safety informed security approaches that consider influence of safety on security; security informed safety approaches that consider influence of security on safety. The results showed that a number of identified approaches are driven by needs in fast developing application areas, e.g., automotive, while works focusing on combined analysis are mostly application area independent. Overall, the study shows that safety and security co-analysis is still a developing domain.

Clock synchronization is one of the most essential assets for distributed real-time systems, as sensing, control and actuation require synchronized communication to meet real-time deadlines. We propose a distributed monitoring method to detect if an adversary is interfering with the clock synchronization protocol. The monitor uses certain network indicators and a set of rules to decide about switching between Normal, Quarantine or Attack Detected states. Further, we propose a way to define thresholds for decision-making based on theoretical analysis of the indicator values influenced by an attack. In addition, we formulate the problem of adversary influence detection in the network as a detection theory problem and use it to derive an additional indicator for the network monitor. Finally, we analyze the time chase between the monitor and an adversary to investigate which factors influence the final outcome.

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