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 Long-term Information Preservation and Access(2010) Song, Sang Chul; JaJa, Joseph F; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An unprecedented amount of information encompassing almost every facet of human activities across the world is generated daily in the form of zeros and ones, and that is often the only form in which such information is recorded. A good fraction of this information needs to be preserved for periods of time ranging from a few years to centuries. Consequently, the problem of preserving digital information over a long-term has attracted the attention of many organizations, including libraries, government agencies, scientific communities, and individual researchers. In this dissertation, we address three issues that are critical to ensure long-term information preservation and access. The first concerns the core requirement of how to guarantee the integrity of preserved contents. Digital information is in general very fragile because of the many ways errors can be introduced, such as errors introduced because of hardware and media degradation, hardware and software malfunction, operational errors, security breaches, and malicious alterations. To address this problem, we develop a new approach based on efficient and rigorous cryptographic techniques, which will guarantee the integrity of preserved contents with extremely high probability even in the presence of malicious attacks. Our prototype implementation of this approach has been deployed and actively used in the past years in several organizations, including the San Diego Super Computer Center, the Chronopolis Consortium, North Carolina State University, and more recently the Government Printing Office. Second, we consider another crucial component in any preservation system - searching and locating information. The ever-growing size of a long-term archive and the temporality of each preserved item introduce a new set of challenges to providing a fast retrieval of content based on a temporal query. The widely-used cataloguing scheme has serious scalability problems. The standard full-text search approach has serious limitations since it does not deal appropriately with the temporal dimension, and, in particular, is incapable of performing relevancy scoring according to the temporal context. To address these problems, we introduce two types of indexing schemes - a location indexing scheme, and a full-text search indexing scheme. Our location indexing scheme provides optimal operations for inserting and locating a specific version of a preserved item given an item ID and a time point, and our full-text search indexing scheme efficiently handles the scalability problem, supporting relevancy scoring within the temporal context at the same time. Finally, we address the problem of organizing inter-related data, so that future accesses and data exploration can be quickly performed. We, in particular, consider web contents, where we combine a link-analysis scheme with a graph partitioning scheme to put together more closely related contents in the same standard web archive container. We conduct experiments that simulate random browsing of preserved contents, and show that our data organization scheme greatly minimizes the number of containers needed to be accessed for a random browsing session. Our schemes have been tested against real-world data of significant scale, and validated through extensive empirical evaluations.Item PROPERTY-BASED INTEGRITY MONITORING OF OPERATING SYSTEM KERNELS(2008-04-03) Petroni, Jr., Nick Louis; Hicks, Michael; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)As the foundation of the trusted computing base, the operating system kernel is a valuable target for attackers of a computer system seeking maximum control and privilege. Furthermore, because the majority of modern security solutions rely on the correctness of at least some portion of the operating system kernel, skilled attackers who successfully infiltrate kernel memory can remain undetected indefinitely. In this dissertation, we present an approach for detecting attacks against the kernel's integrity (commonly referred to as "rootkits"). Our approach, which we call property-based integrity monitoring, works by monitoring and analyzing the kernel's state at runtime. Unlike traditional security solutions, our monitor operates in isolation of, and independently from, the protected operating system and has direct access to the kernel's runtime state. The basic strategy behind property-based monitoring is to identify a set of properties that are practical to check, yet are effective at detecting the types of changes an attacker might make - both known and yet-to-be-discovered. In this work, we describe a practical and effective property for detecting persistent control-flow modifications in running kernels, called state-based control-flow integrity (SBCFI). Furthermore, to address those data-only attacks that do not violate the kernel's control-flow, we introduce a high-level policy language system for enforcing semantic integrity constraints in runtime kernel data. To evaluate the feasibility and effectiveness of our system, we have implemented two property-based integrity monitors for the Linux kernel - one using a virtual machine monitor and the other using a PCI-based coprocessor. We demonstrate that property-based monitoring is capable of detecting all publicly-available kernel integrity threats while imposing less than 1% overhead on the protected system. We conclude that property-based kernel integrity monitoring can be both practical and effective.