Applying the Isabelle Insider Framework to Airplane Security
This work addresses airplane security for safety-critical avionics by integrating human factors into verification, though it is incremental as it extends an existing framework.
The paper tackles the problem of verifying security policies for airplane systems in the presence of insider threats by applying the Isabelle Insider framework, resulting in the development of a methodology for policy development that satisfies stated properties through logical modeling and invariant reasoning.
Avionics is one of the fields in which verification methods have been pioneered and brought a new level of reliability to systems used in safety critical environments. Tragedies, like the 2015 insider attack on a German airplane, in which all 150 people on board died, show that safety and security crucially depend not only on the well functioning of systems but also on the way how humans interact with the systems. Policies are a way to describe how humans should behave in their interactions with technical systems, formal reasoning about such policies requires integrating the human factor into the verification process. In this paper, we report on our work on using logical modelling and analysis of infrastructure models and policies with actors to scrutinize security policies in the presence of insiders. We model insider attacks on airplanes in the Isabelle Insider framework. This application motivates the use of an extension of the framework with Kripke structures and the temporal logic CTL to enable reasoning on dynamic system states. Furthermore, we illustrate that Isabelle modelling and invariant reasoning reveal subtle security assumptions. We summarize by providing a methodology for the development of policies that satisfy stated properties.