I would like to thank Prof. Dr. Torsten Braun, head of the Computer Network and Distributed Systems group (RVS), for supervising this work and for his insightful advises. Prof. Dr. Torsten Braun encouraged and motivated me to publish my research results and he provided me the opportunity to present the work on various conferences, for which I thank him. I would also like to thank Prof. Dr. Roger Wattenhofer, responsible for the Koreferat of this work. Also, Prof. Dr. Oscar Nierstrasz who was willing to be the co-examinator of this work deserves many thanks. Many thanks go to my colleagues of the RVS group and of the IAM for our various interesting discussions about all kinds of topics and for making the institute a very pleasant and friendly place to work at. Special thanks go to David Steiner, Marc Steinemann, Matthias Scheidegger, Florian Baumgartner, Ruy De Oliveira, and Attila Weyland. There are many students who worked with me and helped a lot in developing and implementing. Among them I especially thankful to Thomas Bernoulli,

in this paper: they rely on data and sources presented in the updated version of my trilogy (Castells 2000a). For the sake of clarity, I will rst present the conceptual framework I use in my analysis of social structure. I will then proceed to enumerate the main transformations taking place in social structures

the desperation of users. To establish a secure basis for Internet communication, we propose SafeSlinger, a system leveraging the proliferation of smartphones to enable people to securely and privately exchange their public keys. Through the exchanged authentic public key, SafeSlinger establishes a secure channel

to be performed in a self-organizing manner, securing mobile ad hoc networks become a challenging issue, due to the absence of centralized services, key exchange and so on. This paper introduces a framework called Secure and Self Organizing Key Management (S-SOKM). The framework takes advantage of the self

aimed at enabling secure access to services astride organizational boundaries. Also, Kerberos has continued to evolve as new functionalities are added to the basic protocol and one of well-known these protocols is PKINIT. First, I review and analyze the structure of Kerberos recently proposed

@ Printed on acid-free paper which falls within the guidelines of the ANSI

Mobile users share the same expectations as wired users: they want to communicate with other people, they ex-pect the communication to be secure, and it should all be easy. However, mobility poses many challenges for security. Communication is often ad hoc, and the infras-tructure may be untrusted

Hiermit versichere ich, die vorliegende Diplomarbeit selbstständig und unter ausschliesslicher Verwendung der angegebenen Quellen und Hilfsmittel angefertigt zu haben. Diese Arbeit hat in gleicher oder ähnlicher Form noch keiner Prüfungsbehörde vorgelegen. Darmstadt, 14. Februar 2006

This thesis presents CraneTracker, a multi-modal sensing and communication system for monitoring migratory species at the continental level. By exploiting the robust and extensive cellular infrastructure across the continent, traditional mobile wireless sensor networks can be extended to enable reliable, low-cost monitoring of migratory species. The developed multi-tier architecture yields ecologists with unconventional behavior in-formation not furnished by alternative tracking systems at such a large scale and for a low-cost. The simulation, development and implementation of the CraneTracker soft-ware system is presented. The system is shown effective through multiple proxy deploy-

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