Mapping the Impact of Security Threats on Safety-Critical Global Navigation Satellite Systems

Safety cases provide high-level support for the development of critical systems. They present a graphical overview of arguments and evidence to demonstrate that complex applications are acceptably safe within a particular context of use. This paper shows how safety cases support the application of the latest generation of augmented Global Navigation Satellite Systems (GNSS). Unfortunately, at almost the same time as these satellite-based systems have been approved to provide location and timing information in safety-critical applications, a range of organisations including the UK Ministry of Defence, have raised concerns about our increasing vulnerability to attacks on architectures that depend upon GPS, GLONASS etc. These threats are compounded by the difficulty of representing and reasoning about the impact of jamming, spoofing and insider threats within safety argumentation techniques. Such attacks invalidate many of the assumptions that support the provision of critical services. We show how a risk based approach to the identification of attack scenarios can be used to assess the resilience of safety cases to the impact of external security threats.