Services in a mobile environment are based on the locations of mobile users. Personalization, based on the profiles of mobile users, significantly increases the value of such services. However, they pose significant security and privacy challenges; ensuring security and privacy for a personalized mobile environment in an efficient manner is the primary objective of this dissertation. Often, access control requirements in a mobile environment are based on the spatiotemporal attributes of mobile

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... sers, resources to be protected, profiles of users, or all of these. Evaluating an access request incurs significant overhead as it requires searching for the relevant moving objects that satisfy the query as well as the applicable security policies. In this disserta-tion, we have developed a unified index structure capable of indexing mobile objects, security policies and profiles, in a single index. This enables the efficient enforcement of access control. Another contribution is to extend the enforcement of access control to the case where instead of the exact location, ii only the approximate location of moving objects is maintained. To this end, the dissertation proposes an authorization model that takes the uncertainty of location measures into consideration for specifying and evaluating access control policies. Another pressing issue in delivering mobile services is protecting the privacy of users. In this dissertation, we have proposed a comprehensive family of anonymity models, based on k-anonymity, that incorporates location, direction , as well as profile information. We have also developed anonymization algorithms that can constrain both the generalization of the location as well as that of profiles and direction, while meeting the quality of service requirements. In addition, we have proposed a partitioning method that can limit tracking of the service requestor while continuously receiving a service, thus achieving enhanced level of both privacy and quality of service. iii PREFACE