by Yeung Siu Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 59-[62]). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Background --- p.4 / Chapter 2.1 --- Properties of a digital watermarking system --- p.5 / Chapter 2.2 --- Digital watermarking in still images: Spatial-domain vs Frequency- domain --- p.7 / Chapter 2.3 --- Capacity in digital watermarking --- p.8 / Chapter 3 --- A watermarking system --- p.10 / Chapter 3.1 --- Implementation of a watermarking system --- p.10 / Chapter 3.1.1 --- Embedding watermark --- p.11 / Chapter 3.1.2 --- Detecting watermark --- p.14 / Chapter 3.2 --- Robustness testing on the watermarking system --- p.18 / Chapter 3.3 --- Geometric attacks to the watermark system --- p.18 / Chapter 3.3.1 --- "The three distortions: Translation, Dilation and Rotation" --- p.19 / Chapter 3.3.2 --- The commutative property of rotation and dilation --- p.25 / Chapter 3.3.3 --- Implementation of geometric transform --- p.25 / Chapter 4 --- General Defense on Geometric Distortions --- p.28 / Chapter 4.1 --- Special designed watermark --- p.29 / Chapter 4.1.1 --- Ring-shaped watermark --- p.29 / Chapter 4.1.2 --- Phase Taylor invariance --- p.30 / Chapter 4.1.3 --- "Rotation, dilation and translation invariant watermark" --- p.31 / Chapter 4.2 --- Distortion detection --- p.34 / Chapter 4.2.1 --- Brute-force method --- p.35 / Chapter 4.2.2 --- Interactive method --- p.37 / Chapter 5 --- Specific Defense in Geometric Distortions - Phase angle com- parison --- p.43 / Chapter 5.1 --- Translation Detection --- p.44 / Chapter 5.2 --- Dilation Detection --- p.46 / Chapter 5.3 --- Rotation Detection --- p.49 / Chapter 6 --- Further work --- p.54 / Chapter 6.1 --- Large scale distortion detection --- p.54 / Chapter 6.2 --- Mixed geometric distortions --- p.55 / Chapter 7 --- Conclusion --- p.57 / Bibliography --- p.59

Recently e-Commerce systems have undergone an accelerated development, bringing a new set of risks and issues to government. As a result of this trend processes, policies and practices of organisations have changed dramatically. However, current research into the organisational risks and security in e- Government from an Australian viewpoint continues to be limited. This thesis is concerned with improving our understanding IS Security in e- Government. Key e-Government security issues are identified through a literature review. The results of a review of recent literature, together with investigatory interviews with experts from NSW Government, are used to further refine issues, research questions and propose a model of activity theory within a fuzzy logic framework. The developed model was refined and used to analyse results from the collected survey data, the results allow agencies to be classified by their progress towards accreditation to AS/NZS17799.1:2001. These results were able to be externally validated by another government agencies IS security survey. A series of surveys, forums, and interviews with government e-Commerce security officers were used to further test and refine the model, as well as answer the research questions posed. This study was conducted over a period of three years and identified the key issues in e-Government across a broad cross-section of NSW Government agencies. The results provide, a significant contribution to theory, especially for IS security managers through a more detailed understanding of the perceptions of practitioners. This research improves the level of understanding of IS security within the domain of e-Commerce risks and security within NSW Government by grouping agencies into meaningful categories, documenting successful practices by IS security managers, identifying drivers and inhibitors to IS security, determining the status of IS security across the NSW Government and monitoring the progress of agencies towards accreditation to AS/NZS177999:2001.

We propose a novel approach for detecting visual similarity between two web pages. The proposed approach applies Gestalt theory and considers a webpage as a single indivisible entity. The concept of supersignals, as a realization of Gestalt principles, supports our contention that web pages must be treated as indivisible entities. We objectify, and directly compare, these indivisible supersignals using algorithmic complexity theory. We apply our new approach to the domain of anti-Phishing technologies, which at once gives us both a reasonable ground truth for the concept of “visually similar,” and a high-value application of our proposed approach. Phishing attacks involve sophisticated, fraudulent websites that are realistic enough to fool a significant number of victims into providing their account credentials. There is a constant tug-of-war between anti-Phishing researchers who create new schemes to detect Phishing scams, and Phishers who create countermeasures. Our approach to Phishing detection is based on one major signature of Phishing webpage which can not be easily changed by those con artists –Visual Similarity. The only way to fool this significant characteristic appears to be to make a visually dissimilar Phishing webpage, which also reduces the successful rate of the Phishing scams or their criminal profits dramatically. For this reason, our application appears to be quite robust against a variety of common countermeasures Phishers have employed. To verify the practicality of our proposed method, we perform a large-scale, real-world case study, based on “live” Phish captured from the Internet. Compression algorithms (as a practical operational realization of algorithmic complexity theory) are a critical component of our approach. Out of the vast number of compression techniques in the literature, we must determine which compression technique is best suited for our visual similarity problem. We therefore perform a comparison of nine compressors (including both 1-dimensional string compressors and 2-dimensional image compressors). We finally determine that the LZMA algorithm performs best for our problem. With this determination made, we test the LZMA-based similarity technique in a realistic anti-Phishing scenario. We construct a whitelist of protected sites, and compare the performance of our similarity technique when presented with a) some of the most popular legitimate sites, and b) live Phishing sites targeting the protected sites. We found that the accuracy of our technique is extremely high in this test; the true positive and false positive rates reached 100% and 0.8%, respectively. We finally undertake a more detailed investigation of the LZMA compression technique. Other authors have argued that compression techniques map objects to an implicit feature space consisting of the dictionary elements generated by the compressor. In testing this possibility on live Phishing data, we found that derived variables computed directly from the dictionary elements were indeed excellent predictors. In fact, by taking advantage of the specific characteristic of dictionary compression algorithm, we slightly improve on our accuracy when using a modified/refined LZMA algorithm for our already perfect NCD classification application. / Software Engineering and Intelligent Systems

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisor: Mohamed G. Gouda. Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M.S.)--Wake Forest University. Dept. of Computer Science, 2004. / Includes bibliographical references (leaves 99-100).

Thesis (M.S.)--Florida State University, 2003. / Advisor: Dr. Alec Yasinsac, Florida State University, School of Arts and Sciences, Dept. of Computer Science. Title and description from dissertation home page (viewed Oct. 1, 2003). Includes bibliographical references.

Thesis (M.S. in Computer Science)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Cynthia E. Irvine, Roger R. Schell. Includes bibliographical references (p. 83-92). Also available online.

Thesis (M.S. in Computer Science)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Cynthia E. Irvine, Roger R. Schell. Includes bibliographical references (p. 105-107). Also available online.

Thesis (M.A. in National Security Affairs)--Naval Postgraduate School, June 2003. / Thesis advisor(s): Mikhail Tsypkin, Dorothy Denning. Includes bibliographical references. Also available online.

published_or_final_version / Computer Science / Master / Master of Philosophy