Shen, Yuxiu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 61-64). / Abstracts in Chinese and English. / 摘要........Error! Bookmark not defined / Abstract --- p.iii / Acknowledgement --- p.v / Content --- p.viii / List of Figures --- p.xi / List of Tables --- p.xii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background Overview --- p.1 / Chapter 1.2 --- Motivation and Related Work --- p.2 / Chapter 1.3 --- Our Contribution --- p.3 / Chapter 1.4 --- Organization of the Thesis --- p.5 / Chapter Chapter 2 --- Preliminaries --- p.6 / Chapter 2.1 --- TDMA Technology --- p.6 / Chapter 2.1.1 --- Features of TDMA --- p.8 / Chapter 2.2 --- Previous Study on TDMA Link Scheduling --- p.8 / Chapter 2.3 --- Typical Network and Interference Models --- p.10 / Chapter Chapter 3 --- System Model --- p.14 / Chapter 3.1 --- Physical Layer Interference Model --- p.14 / Chapter 3.2 --- Objective of the Problem --- p.15 / Chapter 3.3 --- Rate Matrices for Transmission Sets --- p.17 / Chapter 3.4 --- Airtime Allocation --- p.19 / Chapter Chapter 4 --- Problem Formulation and Its Solution --- p.20 / Chapter 4.1 --- LP Formulation of Optimal TDMA Link Scheduling --- p.21 / Chapter 4.2 --- Solution to the Optimal Air Time Allocation Problem --- p.22 / Chapter 4.3 --- n-length Chain Network --- p.24 / Chapter 4.3.1 --- Adaptive Rate Transmission --- p.25 / Chapter 4.3.2 --- Fixed Rate Transmission --- p.27 / Chapter Chapter 5 --- Bad Transmission Set Removal Algorithm (BTSR) --- p.30 / Chapter 5.1 --- A 7-node Chain Example --- p.30 / Chapter 5.2 --- BTSR Algorithm --- p.32 / Chapter Chapter 6 --- Randomized Decentralized Scheduling Algorithm (RDSA) --- p.35 / Chapter 6.1 --- RDSA Algorithm --- p.35 / Chapter 6.2 --- Pseudo Code of RDSA --- p.37 / Chapter 6.3 --- The Flow Chart of RDSA --- p.39 / Chapter Chapter 7 --- Performance Evaluation --- p.41 / Chapter 7.1 --- Performance of Cross-layer TDMA Link Scheduling --- p.41 / Chapter 7.2 --- Complexity Analysis and Comparisons for BTSR+LP and LP --- p.46 / Chapter 7.2.1 --- Complexity of LP Problem --- p.47 / Chapter 7.2.2 --- Problem Size Reduced by BTSR --- p.48 / Chapter 7.2.3 --- Revised BTSR Algorithm --- p.49 / Chapter 7.2.4 --- The Complexity Issues --- p.51 / Chapter 7.3 --- Performance and Complexity Issues for RDSA --- p.52 / Chapter Chapter 8 --- Conclusion and Future Work --- p.57 / Chapter 8.1 --- Conclusions --- p.57 / Chapter 8.2 --- Future Work --- p.58 / Bibliography

Sun, Qifu. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 95-99). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

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The MiniCA project is proposed and developed to address growing demand for inexpensive access to security features such as privacy, strong authentication, and digital signatures. These features are integral to public-key encryption technologies. The audience for whom the software project is intended includes, technical staff requiring certificates for use in SSL applications (i.e. a secure web-site) at California State University, San Bernardino.

This thesis is a study of communication protocols (token ring, FDDI, and ISDN), microcontrollers (68HC 1EVB), and fault tolerance schemes. One of the major weaknesses of the token ring network is that if a single station fails, the entire system fails. A scheme involving a combination of hardware and timer interrupts in the software has been designed and implemented which deals with this risk. Software and protocols have been designed and applied to the network to reduce the chance of bit faults in communications. ISDN frame format proved to be exceptional in its capacity to carry echoed data and a large variety of tokens which could be used by the stations to test the data. By its very nature, the token ring supplied another major fault detection device by allowing the data to be returned and tested at its source. The resulting network was successful.

Geographic information systems (GIS) are developing in a rapidly expanding distributed environment. With the ever-increasing growth of computer networks and the Internet in particular, it is imperative that GIS take advantage of distributed data technologies to provide users and applications with shared and improved access to geographic data.Geographic data distribution design is concerned with determining what data gets placed at which computer network sites and involves the issues of data partitioning, allocation and dynamic migration. Partitioning is concerned with how data, or fragments of the data, are apportioned to partitions. These partitions must then be assigned to network sites in an allocation process. Because data usage and access changes by applications in a dynamic environment, migration strategies are necessary to redistribute the data. In order for data distribution to reflect current usage patterns of applications, the design process must obtain and accumulate data usage information from applications.This dissertation first details the predicate fragmentation (PF) model. The core of the model is the PF tree that has been developed and implemented to store and maintain usage information. User predicates, obtained from application queries, are inserted into the tree and primitive predicates can be identified from the tree. These primitive predicates define the fragmentation from which a data distribution can be determined. Predicate insertion and pruning operations are essential to the maintenance of the tree structure.A methodology that uses the PF model to obtain a partitioning, allocation and migration strategy is then outlined. The fragments identified from the PF trees are aggregated into partitions that are then assigned to individual network sites using a site access allocation strategy. A dynamic migration strategy then uses changes in the PF ++ / trees to identify the data that must be migrated to a new site in order to accommodate the changing application environment.The implementation of the geographic data distribution methodology is referred to as GEODDIS. The methodology was tested and evaluated using a mineral occurrence application called GEOMINE which was developed with the ArcInfo GIS. The results indicate that geographic data distribution performs well when successive applications have similar data usage requirements. The implementation of the geographic data distribution methodology is referred to as GEODDIS. The methodology was tested and evaluated using a mineral occurrence application called GEOMINE which was developed with the ArcInfo GIS. The results indicate that geographic data distribution performs well when successive applications have similar data usage requirements. For applications with very different data usage patterns, the performance decreases to the worst case scenario where all the data must be transferred to the site where it is used. The tree pruning and data migration operations are essential to maintaining a PF tree structure and distribution that reflects the current data usage of applications.

Abstract not available

Security protocols provide a communication architecture upon which security-sensitive distributed applications are built. Flaws in security protocols can expose applications to exploitation and manipulation. A number of formal analysis techniques have been applied to security protocols, with the ultimate goal of verifying whether or not a protocol fulfils its stated security requirements. These tools are limited in a number of ways. They are not fully automated and require considerable effort and expertise to operate. The specification languages often lack expressiveness. Furthermore the model checkers often cannot handle large industrial scale protocols due to the enormous number of states generated.Current research is addressing many of the limitations of the older tools by using state-of-the-art search optimisation and modelling techniques. This dissertation examines new ways in which industrial protocols can be analysed and presents abstract communication channels; a method for explicitly specifying assumptions made about the medium over which participants communicate.

Logic programming with answer set semantics has been considered appealing rule-based formalism language and applied in information security areas. In this thesis, we investigate the problems of authorization in distributed environments and security protocol verification and update. Authorization decisions are required in large-scale distributed environments, such as electronic commerce, remote resource sharing, etc. We adopt the trust management approach, in which authorization is viewed as a ‘proof of compliance" problem. We develop an authorization language AL with non-monotonic feature as the policy and credential specification language, which can express delegation with depth control, complex subject structures, both positive and negative authorizations, and separation of duty concepts. The theoretical foundation for language AL is the answer set semantics of logic programming. We transform AL to logic programs and the authorization decisions are based on answer sets of the programs. We also explore the tractable subclasses of language AL. We implement a fine grained access control prototype system for XML resources, in which the language AL¤ simplified from AL is the policy and credential specification language. We define XPolicy, the XML format of AL¤, which is a DTD for the XML policy documents. The semantics of the policy is based on the semantics of language AL. The system is implemented using Java programming. We investigate the security protocol verification problem in provable security approach. Based on logic programming with answer set semantics, we develop a unified framework for security protocol verification and update, which integrates protocol specification, verification and update. The update model is defined using forgetting techniques in logic programming. Through a case study protocol, we demonstrate an application of our approach. / Doctor of Philosophy (PhD)

This thesis presents a complete alternative service composition model named Service Trading Marketplace Network (STAMP-Net). The primary concept is to improve overall system scalability and introduce a fair business scheme for customers and providers. STAPM-Net focuses on designing an architecture based on both technical and business aspect. In STAMP-NET, users remain the ability to choose their preference service providers from potential-provider lists, and service providers are able to compete for the requested services that they can handle. For these purposes, STAMP-Net introduce a concept of 'Service Trading Marketplace Mechanism' which facilitates a problem of 'conflict of interest'; 'Indirect Service Discovery' which allows service providers to the learn existing of services being offered by other service providers; and 'Service Subcontract System' which allows service providers to subcontract any missing service to other potential service providers. In addition, this thesis also present monitor techniques, which are used to ensure the quality of services.