Biblio

This paper studies the synthesis of controllers for cyber-physical systems (CPSs) that are required to carry out complex tasks that are time-sensitive, in the presence of an adversary. The task is specified as a formula in metric interval temporal logic (MITL). The adversary is assumed to have the ability to tamper with the control input to the CPS and also manipulate timing information perceived by the CPS. In order to model the interaction between the CPS and the adversary, and also the effect of these two classes of attacks, we define an entity called a durational stochastic game (DSG). DSGs probabilistically capture transitions between states in the environment, and also the time taken for these transitions. With the policy of the defender represented as a finite state controller (FSC), we present a value-iteration based algorithm that computes an FSC that maximizes the probability of satisfying the MITL specification under the two classes of attacks. A numerical case-study on a signalized traffic network is presented to illustrate our results.

Complex CPS such as UAS got rapid development these years, but also became vulnerable to GPS spoofing, packets injection, buffer-overflow and other malicious attacks. Ensuring the behaviors of UAS always keeping secure no matter how the environment changes, would be a prospective direction for UAS security. This paper aims at presenting a reactive synthesis-based approach to implement the automatic generation of secure UAS controller. First, we study the operating mechanism of UAS and construct a high-Ievel model consisting of actuator and monitor. Besides, we analyze the security threats of UAS from the perspective of hardware, software and data transmission, and then extract the corresponding specifications of security properties with LTL formulas. Based on the UAS model and security specifications, the controller can be constructed by GR(1) synthesis algorithm, which is a two-player game process between UAV and Environment. Finally, we expand the function of LTLMoP platform to construct the automatons for controller in multi-robots system, which provides secure behavior strategies under several typical UAS attack scenarios.

In this paper, we propose a compositional scheme for the construction of abstractions for networks of control systems by using the interconnection matrix and joint dissipativity-type properties of subsystems and their abstractions. In the proposed framework, the abstraction, itself a control system (possibly with a lower dimension), can be used as a substitution of the original system in the controller design process. Moreover, we provide a procedure for constructing abstractions of a class of nonlinear control systems by using the bounds on the slope of system nonlinearities. We illustrate the proposed results on a network of linear control systems by constructing its abstraction in a compositional way without requiring any condition on the number or gains of the subsystems. We use the abstraction as a substitute to synthesize a controller enforcing a certain linear temporal logic specification. This example particularly elucidates the effectiveness of dissipativity-type compositional reasoning for large-scale systems.

We consider a compositional construction of approximate abstractions of interconnected control systems. In our framework, an abstraction acts as a substitute in the controller design process and is itself a continuous control system. The abstraction is related to the concrete control system via a so-called simulation function: a Lyapunov-like function, which is used to establish a quantitative bound between the behavior of the approximate abstraction and the concrete system. In the first part of the paper, we provide a small gain type condition that facilitates the compositional construction of an abstraction of an interconnected control system together with a simulation function from the abstractions and simulation functions of the individual subsystems. In the second part of the paper, we restrict our attention to linear control system and characterize simulation functions in terms of controlled invariant, externally stabilizable subspaces. Based on those characterizations, we propose a particular scheme to construct abstractions for linear control systems. We illustrate the compositional construction of an abstraction on an interconnected system consisting of four linear subsystems. We use the abstraction as a substitute to synthesize a controller to enforce a certain linear temporal logic specification.

Hypergame theory has been used to model advantages in decision making. This research provides a formal representation of deception to further extend the hypergame model. In order to extend the model, we propose a hypergame theoretic framework based on temporal logic to model decision making under the potential for trust and deception. Using the temporal hypergame model, the concept of trust is defined within the constraints of the model. With a formal definition of trust in hypergame theory, the concepts of distrust, mistrust, misperception, and deception are then constructed. These formal definitions are then applied to an Attacker-Defender hypergame to show how the deception within the game can be formally modeled; the model is presented. This demonstrates how hypergame theory can be used to model trust, mistrust, misperception, and deception using a formal model.

SCADA control systems use programmable logic controller to interface with critical machines. SCADA systems are used in critical infrastructures, for instance, to control smart grid, oil pipelines, water distribution and chemical manufacturing plants: an attacker taking control of a SCADA system could cause various damages, both to the infrastructure but also to people (for instance, adding chemical substances into a water distribution systems). In this paper we propose a method to detect attacks targeting SCADA systems. We exploit model checking, in detail we model logs from SCADA systems into a network of timed automata and, through timed temporal logic, we characterize the behaviour of a SCADA system under attack. Experiments performed on a SCADA water distribution system confirmed the effectiveness of the proposed method.

In the development process of critical systems, one of the main challenges is to provide early system validation and verification against vulnerabilities in order to reduce cost caused by late error detection. We propose in this paper an approach that, firstly allows formally describe system security specifications, thanks to our suggested extended attack tree. Secondly, static and dynamic system modeling by using a SysML connectivity profile to model error propagation is introduced. Finally, a model checker has been used in order to validate system specifications.

Security is an important requirement of every reactive system of the smart gird. The devices connected to the smart system in smart grid are exhaustively used to provide digital information to outside world. The security of such a system is an essential requirement. The most important component of such smart systems is Operating System (OS). This paper mainly focuses on the security of OS by incorporating Access Control Mechanism (ACM) which will improve the efficiency of the smart system. The formal methods use applied mathematics for modelling and analysing of smart systems. In the proposed work Formal Security Analysis (FSA) is used with model checking and hence it helped to prove the security of smart systems. When an Operating System (OS) takes into consideration, it never comes to a halt state. In the proposed work a Transition System (TS) is designed and the desired rules of security are provided by using Linear Temporal Logics (LTL). Unlike other propositional and predicate logic, LTL can model reactive systems with a prediction for the future state of the systems. In the proposed work, Simple Promela Interpreter (SPIN) is used as a model checker that takes LTL and TS of the system as input. Hence it is possible to derive the Büchi automaton from LTL logics and that provides traces of both successful and erroneous computations. Comparison of Büchi automaton with the transition behaviour of the OS will provide the details of security violation in the system. Validation of automaton operations on infinite computational sequences verify that whether systems are provably secure or not. Hence the proposed formal security analysis will provably ensures the security of smart systems in the area of smart grid applications.

Wireless sensor networks (WSN) are useful in many practical applications including agriculture, military and health care systems. However, the nodes in a sensor network are constrained by energy and hence the lifespan of such sensor nodes are limited due to the energy problem. Temporal logics provide a facility to predict the lifetime of sensor nodes in a WSN using the past and present traffic and environmental conditions. Moreover, fuzzy logic helps to perform inference under uncertainty. When fuzzy logic is combined with temporal constraints, it increases the accuracy of decision making with qualitative information. Hence, a new data collection and cluster based energy efficient routing algorithm is proposed in this paper by extending the existing LEACH protocol. Extensions are provided in this work by including fuzzy temporal rules for making data collection and routing decisions. Moreover, this proposed work uses fuzzy temporal logic for forming clusters and to perform cluster based routing. The main difference between other cluster based routing protocols and the proposed protocol is that two types of cluster heads are used here, one for data collection and other for routing. In this research work we conducted an experiment and it is observed that the proposed fuzzy cluster based routing algorithm with temporal constrains enhances the network life time reduces the energy consumption and enhances the quality of service by increasing the packet delivery ratio by reducing the delay.