1.1 Private and Public Key Cryptography..................... 5

Abstract not found

Algebraic methods in analyzing

pages 156–175, 2013. [2] Johannes Buchmann, Denise Demirel, and Jeroen van de Graaf. Towards a publicly-verifiable mix-net providing everlasting privacy. In Financial Cryptog-raphy, pages 197–204, 2013. [3] Denise Demirel, Jeroen van de Graaf, and Roberto Araùjo. Improving helios

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First, I would like to thank to Dimka Karastoyanova and Mariano Cilia for all the fruitful discussions, their guidance and support through the course of this project. Thanks also to Prof. Alejandro Buchmann who sponsored my stay at Technische Universität Darmstadt during the spring of 2004. The special thanks go to my advisor, Mariano Cilia, who has made all this possible. Finally, I’d like to thank to my family for all these years of support.

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

I would like to thank some people who were involved in the creation of this thesis: • Berry Schoenmakers of TU Eindhoven for introducing me to the topic of cryptographic voting protocols. • Evangelos Karatsiolis for his work in guiding me through the process of writing this thesis and his constant motivation. • Roberto Samarone Araujo for hours of discussing various protocols with Evengelos and me. • Warren D. Smith for providing with a preliminary version of his upcoming book »How Mathematics can Improve Democracy«. • Ute Günther and Christian Burgmann for their proof-reading. Nonetheless, any remaing errors shall be blamed on me. • Andrea Peter for her love and for cheering me up when I was down. • Last but not least my parents, Jacqueline Herrnkind and Hans Peter Klink – without their love and continuous support, this thesis would never have been written.

Intrusion detection/prevention systems (IDSs/IPSs) heavily rely on signature databases and pattern matching (PM) techniques to identify network attacks. The engines of such systems often employ traditional PM algorithms to search for telltale patterns in network flows. The observations that real-world network traffic is largely legitimate and that telltales manifested by exploits rarely appear in network streams lead us to the proposal of Fingerprinter. This framework integrates fingerprinting and PM methods to rapidly distinguish well-behaved from malicious traffic. Fingerprinter produces concise digests or fingerprints for attack signatures during its programming phase. In its querying phase, the framework quickly identifies attack-free connections by transforming input traffic into its fingerprint space and matching its digest against those of attack signatures. If the legitimacy of a stream cannot be determined by fingerprints alone, our framework uses the Boyer–Moore algorithm to ascertain whether attack signatures appear in the stream. To reduce false matches, we resort to multiple fingerprinting techniques including Bloom–Filter and Rabin–Fingerprint. Experimentation with a prototype and a variety of traces has helped us establish that Fingerprinter significantly accelerates the attack detection process.