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

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    User Behavioral Modeling of Web-based Systems for Continuous User Authentication
    (2015) Milton, Leslie Carrie; Memon, Atif; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Authentication plays an important role in how we interact with computers, mobile devices, the web, etc. The idea of authentication is to uniquely identify a user before granting access to system privileges. For example, in recent years more corporate information and applications have been accessible via the Internet and Intranet. Many employees are working from remote locations and need access to secure corporate files. During this time, it is possible for malicious or unauthorized users to gain access to the system. For this reason, it is logical to have some mechanism in place to detect whether the logged-in user is the same user in control of the user's session. Therefore, highly secure authentication methods must be used. We posit that each of us is unique in our use of computer systems. It is this uniqueness that is leveraged to "continuously authenticate users" while they use web software. To monitor user behavior, n-gram models are used to capture user interactions with web-based software. This statistical language model essentially captures sequences and sub-sequences of user actions, their orderings, and temporal relationships that make them unique by providing a model of how each user typically behaves. Users are then continuously monitored during software operations. Large deviations from "normal behavior" can possibly indicate malicious or unintended behavior. This approach is implemented in a system called Intruder Detector (ID) that models user actions as embodied in web logs generated in response to a user's actions. User identification through web logs is cost-effective and non-intrusive. We perform experiments on a large fielded system with web logs of approximately 4000 users. For these experiments, we use two classification techniques; binary and multi-class classification. We evaluate model-specific differences of user behavior based on coarse-grain (i.e., role) and fine-grain (i.e., individual) analysis. A specific set of metrics are used to provide valuable insight into how each model performs. Intruder Detector achieves accurate results when identifying legitimate users and user types. This tool is also able to detect outliers in role-based user behavior with optimal performance. In addition to web applications, this continuous monitoring technique can be used with other user-based systems such as mobile devices and the analysis of network traffic.
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    Mozart, Pergolesi, Handel?: A Study of Three Forgeries
    (2014) Smith, Erin; King, Richard G; Music; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Forgeries of musical manuscripts are little discussed in the musicological literature, but their serious study can be valuable. This thesis outlines a method for the comprehensive study of music forgeries and shows how that method might be used by examining three autograph forgeries in depth. These forgeries are of Pergolesi's "Non mi negar signora" and Mozart's "Baci amorosi e cari," both at The Library of Congress, and Handel's "Rejoice greatly" from Messiah, in the University of Maryland's Special Collections in the Performing Arts. Tobia Nicotra, a prolific forger from the 1920s and 1930s created the two Library of Congress manuscripts and elements of his forging style are identified. Finally, though J. M. Coopersmith claimed the "Rejoice greatly" forgery was Nicotra's, this study shows that it is not Nicotra's due to differences in the forging methods used.
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    Authentication of Fingerprint Scanners
    (2012) Ivanov, Vladimir Iankov; Baras, John S; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    To counter certain security threats in biometric authentication systems, particularly in portable devices (e.g., phones and laptops), we have developed a technology for automated authentication of fingerprint scanners of exactly the same type, manufacturer, and model. The technology uses unique, persistent, and unalterable characteristics of the fingerprint scanners to detect attacks on the scanners, such as detecting an image containing the fingerprint pattern of the legitimate user and acquired with the authentic fingerprint scanner replaced by another image that still contains the fingerprint pattern of the legitimate user but has been acquired with another, unauthentic fingerprint scanner. The technology uses the conventional authentication steps of enrolment and verification, each of which can be implemented in a portable device, a desktop, or a remote server. The technology is extremely accurate, computationally efficient, robust in a wide range of conditions, does not require any hardware modifications, and can be added (as a software add-on) to systems already manufactured and placed into service. We have also implemented the technology in a demonstration prototype for both area and swipe scanners.
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    EXTRINSIC CHANNEL-LIKE FINGERPRINT EMBEDDING FOR TRANSMITTER AUTHENTICATION IN WIRELESS SYSTEMS
    (2011) Goergen, Nathan Scott; Liu, K.J.Ray; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    We present a physical-layer fingerprint-embedding scheme for wireless signals, focusing on multiple input multiple output (MIMO) and orthogonal frequency division multiplexing (OFDM) transmissions, where the fingerprint signal conveys a low capacity communication suitable for authenticating the transmission and further facilitating secure communications. Our system strives to embed the fingerprint message into the noise subspace of the channel estimates obtained by the receiver, using a number of signal spreading techniques. When side information of channel state is known and leveraged by the transmitter, the performance of the fingerprint embedding can be improved. When channel state information is not known, blind spreading techniques are applied. The fingerprint message is only visible to aware receivers who explicitly preform detection of the signal, but is invisible to receivers employing typical channel equalization. A taxonomy of overlay designs is discussed and these designs are explored through experiment using time-varying channel-state information (CSI) recorded from IEEE802.16e Mobile WiMax base stations. The performance of the fingerprint signal as received by a WiMax subscriber is demonstrated using CSI measurements derived from the downlink signal. Detection performance for the digital fingerprint message in time-varying channel conditions is also presented via simulation.
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    Fast Scalable Peer-to-Peer Lookup Services for Multi-Hop Wireless Networks
    (2008-01-28) Shin, Min-Ho; Arbaugh, William A; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Recent years have seen growing popularity of multi-hop wireless networks such as wireless mesh networks and sensor networks. Such systems require efficient lookup services for reliable system operation such as packet routing, key-discovery, and object lookup. The lack of infrastructure, however, makes the centralized lookup fail to scale in multi-hop wireless networks. For example, consider a citywide wireless mesh network which provides wireless connection service to a number of mobile users. Due to a high volume of user access and inherent vulnerability of wireless links, centralized authentication methods fail to scale. The decentralization of user authentication, however, faces a challenge of key discovery ; how to find the location of user keys. Motivated from the user authentication problem in wireless mesh networks, this dissertation work aims to provide efficient and scalable distributed lookup services for multi-hop wireless networks. Employing the notion of peer-to-peer lookup where each node can both query and respond, I present two different methods: Valley-Walk and Rigs. A loosely-structured scheme Valley-Walk strategically places object copies and locates them efficiently only with a minimal local structure. The Valley-Walk finds target objects in near-optimal hop counts with a moderate number of copies (e.g., 10% the network size) stored in the network. Without a global structure, however, Valley-Walk fails to guarantee the low cost search with a small number of copies. A tightly-structured scheme Rigs (Ring Interval Graph Search) realizes a Distributed Hash Table (DHT) in multi-hop wireless networks. Experimental study shows the limitations of existing DHTs in mult-hop wireless networks due to its independence of underlying topology. Unlike DHT, Rigs constructs a search structure Ring Interval Graph such that queries are forwarded only to local neighbors. Rigs guarantees successful object lookup with near-optimal performance.