Merging Worlds – Aligning Safety and Security

Abstract

Safety and security are important domains in current industrial control systems. While safety protects the human and the system itself from failures, security protects the system from malicious entities and their activities. One is static, admitted, and is not allowed to change over years, the other has to adopt dynamically to changes in the threat landscape. Due to digitalization and the need for more performance and a better maintainability, isolated systems, responsible for controlling signals in the railway domain or a power plant in the energy sector, are connected to large networks, using standard protocols and commercial-off-the-shelf components. Because of this change suddenly IT-Security becomes an important topic and it must be integrated in safety components, which due to the contradicting requirements of the domains can be challenging. In a first approach one could think of designing the safety system and applying security to it as a shell afterwards. Although this approach may be applicable and lead to a useable result, better methods may exist, which result in a more efficient design process and a more secure solution. In our integrated approach security and safety lifecycles are merged and several activities like estimating the impact of an error only must be performed once for both domains. Especially in risk analysis, the derivation of security requirements and the maintenance phase, several processes can be combined and will be shown in this work.