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Abstract
This thesis presents a general theory of system composition for possibilistic 代写留学生论文security properties. It is shown that possibilistic security properties can be viewed as a predicate over the traces that are consistent with a low level observation. We provide a uniform framework for analyzing and comparing these properties. We demonstrate how to determine what security property a system satisfies given the security properties satisfied by its constituent components. Also, we show how to construct a system that satisfies a desired security property. This analysis yields a condition that can be used to determine how a property may emerge under composition. We examine the reasons for the failure of feedback composition and provide necessary and sufficient conditions for determining when feedback composition will fail for all properties based on Generalized Noninterference. Unwinding theorems are given for a large class of security properties.

Acknowledgments
A large number of persons were important in the development of this work. First and foremost, I would like to thank my supervisor, Professor E. S. Lee, for his support, encouragement and patient guidance throughout my graduate studies. My university friends who helped make being a graduate student fun. I would like to acknowledge the support that I have received from the Natural Sciences and Engineering Research Council of Canada (NSERC) during the course of my graduate studies. My parents who without their support, dedication and love I would not be here today. Last, but certainly not least, I would like to thank my wife Keri. Her understanding and love have gotten me through the rough times. It is to her I dedicate this work.

1. Introduction and Overview

1.1. Introduction
Computers have proliferated throughout every aspect of today’s society. Ourreliance on computers to maintain and store everything from our nation’s secrets to thenumber of items an individual purchases is growing rapidly. Information is becoming thesingle most important commodity. It is being bought and sold to the highest bidder.Information about individuals, corporations and governments must not be allowed to beinappropriately disclosed, maliciously altered, or destroyed. The threats that must beprotected against are diverse, such as the disgruntled employee, the corporate spy, evenhackers whose only desire is to inflict hardship on unsuspecting people. A means forcontrolling these and all other attacks is required. Without one the damage to societycould be immense. To provide adequate security it must be possible to construct securecomputer systems.

The ability to derive the properties of an assembly of components from theproperties of its individual constituents is central to being able to design secure computersystems. A system for which this capability exists is said to be a composable system.Unfortunately, an understanding of how to construct such secure computer systems hasbeen unavailable. The goal of this work is to provide the necessary foundations so thatsecure computer systems can be built.

The remainder of this introductory chapter will provide some backgroundinformation and state the thesis of the work.

1.2. Security Properties and Systems
The goals of computer security are easily stated; pre本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。