Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item Hardware Assisted Solutions for Automobile Security(2019) Wang, Qian; Qu, Gang; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In the past couple of decades, many in-vehicle features have been invented and deployed in order to make modern vehicles which not only safer and more reliable but also connected, smarter, and intelligent. Meanwhile, vehicular ad-hoc networks (VANETs) are proposed to provide communications between vehicles and road-side stations as the foundation of the intelligent transportation system to provide efficient and safe transportation. To support these updated functions, a large amount of electronic equipment has been integrated into the car system. Although these add-on functions around vehicles offer great help in driving assistance, they inevitably introduced new security vulnerabilities that threaten the safety of the on-board drivers, passengers and pedestrians. This has been demonstrated by many well-documented attacks either on the in-vehicle bus system or on the wireless vehicular network communications. In this dissertation, we design and implement several hardware-oriented solutions to the arousing security issues on vehicles. More specifically, we focus on three important and representative problems: (1) how to secure the in-vehicle Controller Area Network (CAN), (2) how to secure the communication between vehicle and outside, and (3) how to establish trust on VANETs. Current approaches based on cryptographic algorithms to secure CAN bus violate the strict timing and limited resource constraints for CAN communications. We thus emphasize on the alternate solution of intrusion detection system (IDS) in this dissertation. We explore monitoring the changes of CAN message content or the physical delay of its transmission to detect on the CAN bus. We first propose a new entropy-based IDS following the observation that all the known CAN message injection attacks need to alter the CAN identifier bit. Thus, analyzing the entropy changes of such bits can be an effective way to detect those attacks. Next, we develop a delay-based IDS to protect the CAN network by identifying the location of the compromised Electronic Control Unit (ECU) from the transmission delay difference to two terminals connected to the CAN bus. We demonstrate that both approaches can protect the integrity of the messages on CAN bus leading to a further improve the security and safety of autonomous vehicles. In the second part of this dissertation, we consider Plug-and-Secure, an industrial practice on key management for automotive CAN networks. It has been proven to be information theoretically secure. However, we discover side-channel attacks based on the physical properties of the CAN bus that can leak almost the entire secret key bits. We analyze the fundamental characteristics that lead to such attacks and propose techniques to minimize information leakage at the hardware level. Next, we extend our study from in-vehicle secure CAN communication to the communication between vehicle and outside world. We take the example of the popular GPS spoofing attack and show how we can use the rich information from CAN bus to build a cross-validation system to detect such attacks. Our approach is based on the belief that the local driving data from the in-vehicle network can be authenticated and thus trusted by secure CAN networks mechanisms. Such data can be used to cross-validate the GPS signals from the satellite which are vulnerable to spoofing attacks. We conduct driving tests on real roads to show that our proposed approach can defend both GPS spoofing attacks and location-based attacks on the VANETs. Finally, we propose a blockchain based Anonymous Reputation System (BARS) to establish a privacy-preserving trust model for VANETs. The certificate and revocation transparency is implemented efficiently with the proofs of presence and absence based on the extended blockchain technology. To prevent the broadcast of forged messages, a reputation evaluation algorithm is presented relying on both direct historical interactions of that vehicle and indirect opinions from the other vehicles. This dissertation features solutions to vehicle security problems based on hardware or physical characteristics, instead of cryptographic algorithms. We believe that given the critical timing requirement on vehicular systems and their very limited resource (such as the bandwidth on CAN bus), this will be a very promising direction to secure vehicles and vehicular network.Item Shocks and Cold Fronts in Galaxy Clusters --- Probing the Microphysics of the Intracluster Medium(2018) Wang, Qian; Mushotzky, Richard; Markevitch, Maxim; Astronomy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Shocks and cold fronts in galaxy clusters, the largest gravitationally bound systems in the universe, are astrophysical laboratories where we can study the microphysics of the intracluster medium (ICM), a very hot ($T\sim10^7$--$10^8$~K) plasma. Being the main baryon content of galaxy clusters, the ICM plays an important role in mediating the energy cascade from gravitational collapse during cosmological structure formation. It is also intricately linked to the evolution of the galaxies within. The scientific enquiries concerning the ICM range from fundamental physics questions to cosmological measurements. In this dissertation, I demonstrate probing ICM microphysics by studying deep X-ray observations of two galaxy clusters, A520 and A2142. For A520, tests for thermal conduction, electron--ion equilibration timescale, and particle acceleration at the shock were carried out. For A2142, a test for the effective viscosity was performed using two apparent Kelvin-Helmholtz eddies along its southern cold front. Other interesting features were discovered and analyzed, such as a low gas fraction subcluster in the A520 outskirts, and X-ray deficient channels that could be plasma depletion sheets in both clusters.Item THE ANTIVIRAL ROLES OF ATG1 IN DROSOPHILA MELANOGASTER: IMMUNE RESPONSES AGAINST DROSOPHILA X VIRUS(2014) Wang, Qian; Wu, Louisa; Molecular and Cell Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In mammals, autophagy is important for the immune response against select viruses and is responsible for delivering virus to the lysosome for degradation. In Drosophila melanogaster, the roles of autophagy genes in an antiviral immune response are not fully understood. Here we identify a novel antiviral role for Atg1 in Drosophila melanogaster upon infection with Drosophila X virus (DXV). Flies with a decreased level of Atg1 expression in the fat body developed an increased susceptibility to DXV and have a higher viral load compared to wildtype. However, silencing of other autophagy components (Atg7, Atg8) does not have the same effect. Moreover, we could find no evidence that classical autophagy is directly associated with DXV upon viral infection. This suggests that the antiviral function of Atg1 may be independent of classical autophagy. To address this, we examined the effect of Atg1 knockdown on the fly transcriptome in both DXV infected and uninfected flies. Interestingly, lipid droplet lipolysis and β-oxidation, two major processes responsible for energy production, are induced upon DXV infection. Facilitating lipolysis by knocking down lsd2, a positive regulator of lipase bmm, results in an increased host susceptibility to DXV, together with an increased viral load. In contrast, blocking lipolysis in the negative regulator lsd1 null mutant renders the host more resistant to the virus. This indicates that the increased energy production favors the virus for active replication and does not favor the elimination of virus. Surprisingly, silencing of Atg1, even in the absence of infection, also increases the rates of lipolysis and &beta-oxidation, shown by an increased expression of genes that are involved in lipid metabolism and an decreased lipid droplet size in the Atg1-silenced flies. The differences in gene expression and lipid droplet size between Atg1 RNAi flies and WT flies become more apparent as the infection progresses. In summary, we identify a novel role for Atg1 in restricting energy production and limiting DXV replication. This finding may shed light on antiviral studies against other dsRNA viruses that manipulate host energy homeostasis. Finally, our data reveal an important and unexpected role for Atg1 in innate immune antiviral responses independent of autophagy.