The digitalization of safety-critical railroad infrastructure enables new types of attacks. This increases the need to integrate Information Technology (IT) security measures into railroad systems. For that purpose, we rely on a security architecture for a railway object controller which controls field elements that we developed in previous work. Our architecture enables the integration of security mechanisms into a safety-certified railway system. In this paper, we demonstrate the practical feasibility of our architecture by using a Trusted Platform Module (TPM) 2.0 and a Multiple Independent Levels of Safety and Security (MILS) Separation Kernel (SK) for our implementation. Our evaluation includes a test bed and shows how certification and homologation can be achieved.

In this paper, we introduce Userspace Software Integrity Measurement (USIM) for the Linux OS. USIM enables interpreters to measure, log, and irrevocably anchor critical events in the Trusted Platform Module (TPM). We develop a software library in C which provides TPM-based measurement functionality as well as the USIM service, which provides concurrent access handling to the TPM based event logging. Further, we develop and implement a concept to realize highly frequent event logging on the slow TPM. We integrate this library into the Java Virtual Machine (JVM) to measure Java classes and show that it can be easily integrated into other interpreters. With performance measurements we demonstrate that our contribution is feasible and that overhead is negligible.

In this paper we analyze existing work on TPM-based remote attestation for virtualized environments and discuss benefits as well as shortcomings. We identify an approach that provides adequate security and is easy to implement but is prone to relay attacks. We improve that approach by developing countermeasures, while maintaining existing security guarantees. We implement and evaluate on production-grade hardware. With performance measurements and further evaluations we show that our solution is viable.