To be resilient, a system must be adaptable. Trustworthy adaptation requires that a system can be dynamically reconfigured at runtime without compromising the robustness and integrity of the system. Traditional certification practices have conservatively required critical systems to be static, and required assessment of the entire integrated system for certification. Adaptability has been at odds with certification. Adaptive MILS will extend MILS, a successful paradigm for rigorously developed and assured composable static systems, with adaptation mechanisms and a framework within which those mechanisms may be safely and securely employed for reconfiguration within the constraints of a configuration policy.
The Need for Trustworthy Adaptive Systems
Critical infrastructures, systems of autonomous systems, cloud computing for safety- and security-critical applications, are all dynamic systems that demand reliability, robustness, resilience, security, and other attributes we refer to generically as dependability. These systems while proving highassurance must be developed, certified, deployed, and maintained at an affordable cost. Moreover, the modern environment has become hostile for the critical infrastructures requiring constantly adapting their safety and security behaviour.
Extending MILS to Adaptive Systems
MILS is a component-based approach to develop and certify critical systems. Current MILS implementations provide only for fixed runtime architectures as they are based on statically configured MILS platforms. That is, the configuration information used to configure the exported resources of the separation kernel, and other MILS resource-sharing foundational components making up the MILS platform, is finalized before initialization of the MILS platform. After initialization there is no creation or destruction of exported resources, and no changes in the information flow policy. This is a characteristic shared with safety-critical real-time operating systems (RTOSs). The rationale, inherited from the safety domain, is that only static systems can be adequately well understood and analyzed to achieve the required level of confidence that they will behave as expected. The approach has also been applied to security-critical systems needing the highest levels of assurance. A MILS platform that implements a full and flexible ability to change its configuration during runtime is said to be dynamic.
The CITADEL project has built upon the MILS technology accomplishments of D-MILS and Euro-MILS, and performed the research and development necessary to create adaptive MILS systems. We propose to use adaptive MILS in new and evolving adaptive systems contexts having strategic focus within the EU, such as Critical Infrastructures and the Internet of Things, where adaptability is a crucial ingredient for the safety and security of future systems, and where the rigorous construction and verification made possible by MILS holds particular promise.
The project has achieved in its final phase the demonstration of the capabilities of the adaptive MILS technology in several industrial contexts and application scenarios, and has layed the technical foundations for a certification framework for the use of adaptive MILS components and systems in critical infrastructure applications.
CITADEL is an Innovation Action partly funded by the Horizon 2020 Programme of the European Union under grant agreement no. 700665.