Border Patrol: Improving Smart Device Security through Type-Aware Systems Design

There are increasing concerns about the safety and security of critical infrastructure such as nuclear power plants, the electricity grid and other utilities in the face of possible cyber attacks. As ageing controllers are replaced by smart devices based on Field-Programmable Gate Arrays (FPGAs) and embedded microprocessors, the safety of such devices raises many concerns. In particular, there is the very real risk of malicious functionality hidden in the silicon or in software binaries, dormant and waiting to be activated. Current
hardware and software systems are of such complexity that it is impossible to discover such malicious code through testing.

We aim to address this problem by closely connecting the system design specification with the actual implementation through the use of a formal design methodology based on type systems with static and dynamic type checking. The type system will be used as a formal language to encode the design specification so that the actual implementation will automatically be checked against the specification.

Static type checking of data types and multiparty session types can ensure the correctness of the interaction between the components. However, as static checking assume full access to the design source code it cannot be used to protect against potential threads issuing from third-party functional blocks (know as ``Intellectual Property Cores'' or IP cores) that are commonly used in hardware design:
the provider of the IP core can claim adherence to the types and protocols, so that the IP core will meet the compile-time requirements, but the run-time the behaviour cannot be controlled using static techniques. The same applies to third-party compiled software libraries.
Therefore we propose to use run-time checking of data types as well as session types at the boundaries of untrusted modules ("Border Patrol"), so that any intentional or unintentional
breach of the specification will safely be intercepted.

Realising our vision will lead to a revolution in the programming of FPGA-based Systems-on-Chip in particular and embedded systems in general. Progress in the area of systems security is essential to ensure trust in critical infrastructure (e.g. controllers for nuclear power plants) as well as consumer products (cars, smart household appliances). Thanks to the strong theoretical foundations of our work, our methodology will provide very string guarantees about system security. Adoption of our approach into standards for embedded systems would have a very significant impact by removing the security concerns related to the adoption of such systems.

Our proposed work will lead to highly novel compiler technologies, based on a sound formal foundation with guarantees for systems integrity. Not only will our approach make systems more secure, it will also make application development more efficient..

In a nutshell, our methodology encodes the design specification of the system in the type system, so that it is not possible to design a system implementation that does not conform to the formal specification. There is a clear need for more secure systems design, driven by the sectors mentioned above: protection of critical infrastructure is becoming more and more important not only because of the increased threat level but also because aging controller are being replaced with smart devices. The Internet of Things promises a revolution in the home by allowing us a high degree of remote control over our appliances, but security is crucial because compromising such systems could lead to nightmare scenarios. The same is true for the automotive industry: already embedded systems in cars have been hacked, demonstrating the need for a more secure desing approach.

The applications domain for our work is very broad, both in terms of the sectors where smart devices and FPGA-based systems are deployed (much wider than the three examples cited above) but also in terms of applications that are not security related. The obvious one is safety, because our approach makes systems more safe as well as more secure. But apart from that, the adoption of the advanced type systems we propose into design tools and methodologies will make systems design more efficient as well: by dramatically reducing the amount of errors and catching the errors much sooner in the design phase, the debugging times will be reduced very considerably.

Impact of our work will result primarily from adoption of our approach in industry and academia. The Pathways to Impact document explains how we will achieve this impact.