How secure is ERTMS?

This paper reports on the results of a security analysis of the European Railway Traffic Management System (ERTMS) specifications. ERTMS is designed to be fail-safe and the general philosophy of ‘if in doubt, stop the train’ makes it difficult to engineer a train accident. However, it is possible to exploit the fail-safe behaviour of ERTMS and create a situation that causes a train to halt. Thus, denial of service attacks are possible, and could be launched at a time and place of the attacker’s choosing, perhaps designed to cause maximum disruption or passenger discomfort. Causing an accident is more difficult but not impossible

Reducing V&V Cost of Flight Critical Systems: Myth or Reality?

This paper presents an overview of NASA research program on the V&V of flight critical systems. Five years ago, NASA started an effort to reduce the cost and possibly increase the effectiveness of V&V for flight critical systems. It is the right time to take a look back and realize what progress has been made. This paper describes our overall approach and the tools introduced to address different phases of the software lifecycle. For example, we have improved testing by developing a statistical learning approach tor defining test cases. The tool automatically identifies possible unsafe conditions by analyzing outliers in output data; using an iterative learning process, it can then generate more test cases that represent potentially unsafe regions of operation. At the code level, we have developed and made available as open source a static analyzer for C and C++ programs called IKOS. We have shown that IKOS is very precise in the analysis of embedded C programs (very few false positives) and a bit less for regular C and C++ code. At the design level, in collaboration with our NRA partners, we have developed a suite of analysis tools for Simulink models. The analysis is done in a compositional framework for scalability

The Last Decade in Review: Tracing the Evolution of Safety Assurance Cases through a Comprehensive Bibliometric Analysis

Safety assurance is of paramount importance across various domains, including automotive, aerospace, and nuclear energy, where the reliability and acceptability of mission-critical systems are imperative. This assurance is effectively realized through the utilization of Safety Assurance Cases. The use of safety assurance cases allows for verifying the correctness of the created systems capabilities, preventing system failure. The latter may result in loss of life, severe injuries, large-scale environmental damage, property destruction, and major economic loss. Still, the emergence of complex technologies such as cyber-physical systems (CPSs), characterized by their heterogeneity, autonomy, machine learning capabilities, and the uncertainty of their operational environments poses significant challenges for safety assurance activities. Several papers have tried to propose solutions to tackle these challenges, but to the best of our knowledge, no secondary study investigates the trends, patterns, and relationships characterizing the safety case scientific literature. This makes it difficult to have a holistic view of the safety case landscape and to identify the most promising future research directions. In this paper, we, therefore, rely on state-of-the-art bibliometric tools(e.g., VosViewer) to conduct a bibliometric analysis that allows us to generate valuable insights, identify key authors and venues, and gain a birds eye view of the current state of research in the safety assurance area. By revealing knowledge gaps and highlighting potential avenues for future research, our analysis provides an essential foundation for researchers, corporate safety analysts, and regulators seeking to embrace or enhance safety practices that align with their specific needs and objectives

Formal Assurance Arguments: A Solution In Search of a Problem?

An assurance case comprises evidence and argument showing how that evidence supports assurance claims (e.g., about safety or security). It is unsurprising that some computer scientists have proposed formalizing assurance arguments: most associate formality with rigor. But while engineers can sometimes prove that source code refines a formal specification, it is not clear that formalization will improve assurance arguments or that this benefit is worth its cost. For example, formalization might reduce the benefits of argumentation by limiting the audience to people who can read formal logic. In this paper, we present (1) a systematic survey of the literature surrounding formal assurance arguments, (2) an analysis of errors that formalism can help to eliminate, (3) a discussion of existing evidence, and (4) suggestions for experimental work to definitively answer the question

A system-theoretic safety engineering approach for software-intensive systems

In the software development process, formal verification and functional testing are complementary approaches which are used to verify the functional correctness of software; however, even perfectly reliable software could lead to an accident. The correctness of software cannot ensure the safe operation of safety-critical software systems. Therefore, developing safety-critical software requires a more systematic software and safety engineering process that enables the software and safety engineers to recognize the potential software risks. For this purpose, this dissertation introduces a comprehensive safety engineering approach based on STPA for Software-Intensive Systems, called STPA SwISs, which provides seamless STPA safety analysis and software safety verification activities to allow the software and safety engineers to work together during the software development for safety-critical systems and help them to recognize the associated software risks at the system level

A systematic development of a secure architecture for the European Rail Traffic Management System

The European Rail Traffic Management System (ERTMS) is a new signalling scheme that is being implemented worldwide with the aim of improving interoperability and cross-border operation. It is also an example of an Industrial Control System, a safety-critical system which, in recent years, has been subject to a number of attacks and threats. In these systems, safety is the primary concern of the system designers, whilst security is sometimes an afterthought. It is therefore prudent to assure the security for current and future threats, which could affect the safe operation of the railway. In this thesis, we present a systematic security analysis of parts of the ERTMS standard, firstly reviewing the security offered by the protocols used in ERTMS using the ProVerif tool. We will then assess the custom MAC algorithm used by the platform and identify issues that exist in each of the ERTMS protocol layers, and aim to propose solutions to those issues. We also identify a challenge presented by the introduction of ERTMS to National Infrastructure Managers surrounding key management, where we also propose a novel key management scheme, TRAKS, which reduces its complexity. We then define a holistic process for asset owners to carry out their own security assessments for their architectures and consider the unique challenges that are presented by Industrial Control Systems and how these can be mitigated to ensure security of these systems. Drawing conclusions from these analyses, we introduce the notion of a `secure architecture' and review the current compliance of ERTMS against this definition, identifying the changes required in order for it to have a secure architecture, both now and also in the future