Resilience estimation of cyber-physical systems via quantitative metrics

ABSTRACT: This paper is about the estimation of the cyber-resilience of CPS. We define two new resilience estimation metrics: k-steerability and l -monitorability. They aim at assisting designers to evaluate and increase the cyber-resilience of CPS when facing stealthy attacks. The k-steerability metric reflects the ability of a controller to act on individual plant state variables when, at least, k different groups of functionally diverse input signals may be processed. The l -monitorability metric indicates the ability of a controller to monitor individual plant state variables with l different groups of functionally diverse outputs. Paired together, the metrics lead to CPS reaching (k, l )-resilience. When k and l are both greater than one, a CPS can absorb and adapt to control-theoretic attacks manipulating input and output signals. We also relate the parameters k and l to the recoverability of a system. We define recoverability strategies to mitigate the impact of perpetrated attacks. We show that the values of k and l can be augmented by combining redundancy and diversity in hardware and software, in order to apply the moving target paradigm. We validate the approach via simulation and numeric results

Resilience properties and metrics: how far have we gone?

Aim: Resilience is discussed among researchers and practitioners for several decades, but its definition has been questioned even recently and many methods are proposed to evaluate the resilience of systems. This paper presents a review of historic and recent research articles that define and/or propose a way to measure resilience of systems.Methods: While definitions are classified according to the ideas they focus on, different categories of metrics are described, such as quantitative or qualitative approaches.Results: This paper points out that many metrics tend to valuate resilience similarly. In fact, they are generally built upon a specific definition. On the other hand metrics can also be really heterogeneous and do not capture the same meaning of system resilience when different definitions of resilience are considered.Conclusion: This paper aims at gathering and comparing metrics and definitions of resilience in order to determine the origins of the particularities and classify them according to the attributes they take into account