Title: Exhaustive Search and Resolution of OT Puzzles in Real-Time Collaborative Editing Systems

Critical infrastructure is undergoing a fundamental change worldwide in areas such as power, water, transport, defence, etc. Control systems that were previously physicallyisolated and constructed from purpose-built components are increasingly being standardised and interconnected, exposing them to corporate networks and even the Internet. Consequently, well-established ways of engineering systems for safety and reliability are now being forced to address the additional demands of information security. Having conducted research into a variety of safety-critical, mission-critical and security-critical systems, we reflect here on the different emphases they place on basic system requirements. For example, some properties, such as availability, have much higher importance for safety-critical systems than security-critical ones. By contrast, where data confidentiality is the primary concern of a security-critical system, it may be of lower priority in a safety-critical context, and so on. We also review and contrast some widely-cited design principles for critical systems to identify their commonalities and differences. For instance, where a mission-critical system may emphasise ease-of-access for system maintenance, this directly contradicts the security principle of minimising the exposed attack surface. Similarly, while duplicating components can improve reliability it simultaneously creates more opportunities for security violations. Ultimately we conclude not that the worlds of safety, mission and security-critical system engineering are on a disastrous collision course, but rather that the growing complexity of our critical infrastructure means that system developers are now obliged to consider carefully all three perspectives. Biography: Dr. Colin Fidge is a full professor in the Science and Engineering Faculty of the Queensland University of Technology where he teaches software development and scientific research principles. His research interests include high-integrity systems engineering for safety, mission and security-critical applications. His research spans a broad range of systems development tasks including requirements specification, software analysis, and system modelling and simulation. He has conducted research on critical systems for the Defence Science and Technology Organisation, Telstra, Powerlink Queensland, Delta Electricity, NICTA, and the Australian Signals Directorate.