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Dissertation/Thesis Abstract

Cross-Layer Design for Secure and Resilient Control of Cyber-Physical Systems in Smart Cities
by Xu, Zhiheng, Ph.D., New York University Tandon School of Engineering, 2018, 225; 10840627
Abstract (Summary)

With the rapid development of smart cities, there is a growing need to integrate the physical systems, ranging from large-scale infrastructures to small embedded systems, with networked communications. The integration of the physical and cyber systems forms a Cyber-Physical System (CPS). The architecture of cyber-physical systems brings many advantages. For example, the cyber networks facilitate the information exchange among multiple systems. Despite the benefits of a CPS, its cyber-physical nature exposes the system to cyber-physical attacks, which aim to damage the physical layer (e.g., physical devices and equipment) through the cyber network. Even though researchers have studied cybersecurity issues for decades, it is challenging to use traditional technologies to protect CPSs due to the cyber-physical feature. For instance, in general, the conventional information technologies are insufficient to guarantee control performance of the physical layer.

Due to the new challenges in CPSs, in Part I, we introduce a cross-layer design to achieve security and resilience for CPSs. In our basic framework, we combine various technical tools and methods to capture the different properties between cyber and physical layers. In Part II, we address the challenging of the cloud-enabled systems (e.g., networked sensing systems or control systems), which outsources their massive computations to a cloud server with extensive computational resources. The cloud-enabled systems introduce new challenges, which arise from the trustworthiness of the cloud and the cyber-physical connections between the control system and the cloud. To address issues, we use leverage control theory and cryptography to develop secure mechanisms for different layers. For control systems, we use a Model Predictive Control (MPC) approach to develop the controller. For large-scale sensing networks, we use a Kalman filter to achieve massive data assimilation. To guarantee security in the outsourcing process, we establish homomorphic encryption based on the customized and standard encryption scheme. The homomorphic encryption allows the cloud-enabled systems to achieve data privacy during the outsourcing process. Finally, we use an Unmanned Aerial Vehicle (UAV) and a large-scale sensing network in our numerical experiments to corroborate our analytical results.

The growing complexity of CPS makes it challenging and costly to achieve perfect security. Hence, we aim to find the optimal protection for the systems based on limited resources. Game theory provides mathematical tools and models for investigating multiple strategic decision making, where decision makers compete for a resource. In Part III, we use game analytical tools to develop cross-layer strategies to defend the CPSs from specific attacks. Due to the features of specific applications, we use different game models to establish security mechanisms based on various requirements.

The first application based on the game framework is the networked 3D printer. As a result of the high costs of 3D-printing infrastructure, outsourcing the production to third parties specializing in the 3D-printing process becomes necessary. The integration of a 3D-printing system with networked communications constitutes a cyber-physical system, bringing new security challenges. Adversaries can explore the vulnerabilities of networks to damage the physical parts of the system. To address the issues, at the physical layer, we use a Markov jump system to model the system and develop a robust control policy to deal with uncertainties. At the cyber-layer, we use a FlipIt game to model the contention between the defender and attacker for the control of the 3D-printing system. To connect these two layers, we develop a Stackelberg framework to capture the interactions between cyber-layer attacker and defender game and the physical-layer controller and disturbance game and define a new equilibrium concept that captures interdependence of the zero-sum and FlipIt games. We present numerical examples to demonstrate the computation of the equilibria and design defense strategies for 3D printers as a tradeoff between security and robustness.

The second one is the train control system. To meet the increasing railway-transportation demand, researchers have designed a new train control system, communication-based train control (CBTC) system, to maximize the ability of train lines by reducing the headway of each train. However, the wireless communications expose the CBTC system to new security threats. Due to the cyber-physical nature of the CBTC system, a jamming attack can damage the physical part of the train system by disrupting the communications. To address this issue, we develop a secure framework to mitigate the impact of the jamming attack based on a security criterion. At the cyber layer, we use a multi-channel model to enhance the reliability of the communications and develop a zero-sum stochastic game to capture the interactions between the transmitter and jammer. We present analytical results and use dynamic programming to find the equilibrium of the stochastic game. (Abstract shortened by ProQuest.)

Indexing (document details)
Advisor: Zhu, Quanyan
Commitee: Jiang, Zhong-Ping, Selesnick, Ivan
School: New York University Tandon School of Engineering
Department: Electrical and Computer Engineering
School Location: United States -- New York
Source: DAI-B 80/05(E), Dissertation Abstracts International
Subjects: Engineering, Electrical engineering
Keywords: Cross-layer design, Cyber-physical systems, Resilience, Security, Smart cities
Publication Number: 10840627
ISBN: 978-0-438-77872-6
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