@inproceedings{253, abstract = {{Group signatures, introduced by Chaum and van Heyst [15], are an important primitive in cryptography. In group signature schemes every group member can anonymously sign messages on behalf of the group. In case of disputes a dedicated opening manager is able to trace signatures - he can extract the identity of the producer of a given signature. A formal model for static group signatures schemes and their security is defined by Bellare, Micciancio, and Warinschi [4], the case of dynamic groups is considered by Bellare, Shi, and Zhang [5]. Both models define group signature schemes with a single opening manager. The main difference between these models is that the number of group members in static schemes is fixed, while in dynamic schemes group members can join the group over time.}}, author = {{Blömer, Johannes and Juhnke, Jakob and Löken, Nils}}, booktitle = {{Proceedings of the Sixth International Conference on Mathematical Aspects of Computer and Information Sciences (MACIS)}}, pages = {{166--180}}, title = {{{Short Group Signatures with Distributed Traceability}}}, doi = {{10.1007/978-3-319-32859-1_14}}, year = {{2015}}, } @article{284, abstract = {{In this work, we present the first scalable distributed information system, that is, a system with low storage overhead, that is provably robust against denial-of-service (DoS) attacks by a current insider. We allow a current insider to have complete knowledge about the information system and to have the power to block any ϵ-fraction of its servers by a DoS attack, where ϵ can be chosen up to a constant. The task of the system is to serve any collection of lookup requests with at most one per nonblocked server in an efficient way despite this attack. Previously, scalable solutions were only known for DoS attacks of past insiders, where a past insider only has complete knowledge about some past time point t0 of the information system. Scheideler et al. [Awerbuch and Scheideler 2007; Baumgart et al. 2009] showed that in this case, it is possible to design an information system so that any information that was inserted or last updated after t0 is safe against a DoS attack. But their constructions would not work at all for a current insider. The key idea behind our IRIS system is to make extensive use of coding. More precisely, we present two alternative distributed coding strategies with an at most logarithmic storage overhead that can handle up to a constant fraction of blocked servers.}}, author = {{Eikel, Martina and Scheideler, Christian}}, journal = {{Transactions on Parallel Computing}}, number = {{3}}, pages = {{18:1----18:33}}, publisher = {{ACM}}, title = {{{IRIS: A Robust Information System Against Insider DoS Attacks}}}, doi = {{10.1145/2809806}}, year = {{2015}}, } @misc{286, author = {{Kalde, Benedikt}}, publisher = {{Universität Paderborn}}, title = {{{Implementierung eines hybriden Verschlüsselungsverfahrens nach Cramer und Shoup}}}, year = {{2015}}, } @misc{261, author = {{Eisenhofer, Thorsten}}, publisher = {{Universität Paderborn}}, title = {{{Protokolle zur authentifizierten Schüsselvereinbarung}}}, year = {{2015}}, } @misc{321, author = {{Eidens, Fabian}}, publisher = {{Universität Paderborn}}, title = {{{Anonymous credential system based on q-Strong Diffie-Hellman Assumption}}}, year = {{2015}}, } @inproceedings{322, abstract = {{Reputation systems are used to compute and publish reputation scores for services or products. We consider reputation systems where users are allowed to rate products that they purchased previously. To obtain trustworthy reputations, they are allowed to rate these products only once. As long as users rate products once, they stay anonymous. Everybody is able to detect users deviating from the rate-products-only-once policy and the anonymity of such dishonest users can be revoked by a system manager. In this paper we present formal models for such reputation systems and their security. Based on group signatures presented by Boneh, Boyen, and Shacham we design an efficient reputation system that meets all our requirements.}}, author = {{Blömer, Johannes and Juhnke, Jakob and Kolb, Christina}}, booktitle = {{Proceedings of the 18th International Conference on Financial Cryptography and Data Security (FC)}}, pages = {{478----488}}, title = {{{Anonymous and Publicly Linkable Reputation Systems}}}, doi = {{10.1007/978-3-662-47854-7_29}}, year = {{2015}}, } @misc{325, author = {{Löken, Nils}}, publisher = {{Universität Paderborn}}, title = {{{A Group Signature Scheme with Distributed Group Management - An Application of Threshold Encryption}}}, year = {{2015}}, } @misc{326, author = {{Heihoff, Frederic}}, publisher = {{Universität Paderborn}}, title = {{{A group signature scheme based on the LSRW assumption}}}, year = {{2015}}, } @misc{297, author = {{Sosniak, Martin}}, publisher = {{Universität Paderborn}}, title = {{{Evaluation of Pairing Optimization for Embedded Platforms}}}, year = {{2015}}, } @misc{299, author = {{Gerken, Britta}}, publisher = {{Universität Paderborn}}, title = {{{Elektromagnetische Seitenkanalangriffe auf paarungsbasierte Kryptographie}}}, year = {{2015}}, } @misc{301, author = {{Bobolz, Jan}}, publisher = {{Universität Paderborn}}, title = {{{Efficient Verifier-Local Revocation for Anonymous Credentials}}}, year = {{2015}}, } @misc{302, author = {{Stroh, Christian}}, publisher = {{Universität Paderborn}}, title = {{{Efficient Attributes for Pairing-Based Anonymous Credentials}}}, year = {{2015}}, } @phdthesis{305, author = {{Kniesburges, Sebastian}}, publisher = {{Universität Paderborn}}, title = {{{Distributed Data Structures and the Power of topological Self-Stabilization}}}, year = {{2015}}, } @misc{312, author = {{Schleiter, Patrick}}, publisher = {{Universität Paderborn}}, title = {{{Constructions of Fully Secure Predicate Encryption Schemes}}}, year = {{2015}}, } @misc{273, author = {{Kohn, Kathlén}}, publisher = {{Universität Paderborn}}, title = {{{Number of Voronoi-relevant vectors in lattices with respect to arbitrary norms}}}, year = {{2015}}, } @techreport{233, abstract = {{Motivated by the deterministic single exponential time algorithm of Micciancio and Voulgaris for solving the shortest and closest vector problem for the Euclidean norm, we study the geometry and complexity of Voronoi cells of lattices with respect to arbitrary norms.On the positive side, we show that for strictly convex and smooth norms the geometry of Voronoi cells of lattices in any dimension is similar to the Euclidean case, i.e., the Voronoi cells are defined by the so-called Voronoi-relevant vectors and the facets of a Voronoi cell are in one-to-one correspondence with these vectors. On the negative side, we show that combinatorially Voronoi cells for arbitrary strictly convex and smooth norms are much more complicated than in the Euclidean case.In particular, we construct a family of three-dimensional lattices whose number of Voronoi-relevant vectors with respect to the l_3-norm is unbounded.Since the algorithm of Micciancio and Voulgaris and its run time analysis crucially dependonthefactthatfortheEuclidean normthenumber of Voronoi-relevant vectors is single exponential in the lattice dimension, this indicates that the techniques of Micciancio and Voulgaris cannot be extended to achieve deterministic single exponential time algorithms for lattice problems with respect to arbitrary l_p-norms.}}, author = {{Blömer, Johannes and Kohn, Kathlén}}, publisher = {{Universität Paderborn}}, title = {{{Voronoi Cells of Lattices with Respect to Arbitrary Norms}}}, year = {{2015}}, } @inproceedings{346, abstract = {{One future goal of service-oriented computing is to realize global markets of composed services. On such markets, service providers offer services that can be flexibly combined with each other. However, most often, market participants are not able to individually estimate the quality of traded services in advance. As a consequence, even potentially profitable transactions between customers and providers might not take place. In the worst case, this can induce a market failure. To overcome this problem, we propose the incorporation of reputation information as an indicator for expected service quality. We address On-The-Fly Computing as a representative environment of markets of composed services. In this environment, customers provide feedback on transactions. We present a conceptual design of a reputation system which collects and processes user feedback, and provides it to participants in the market. Our contribution includes the identification of requirements for such a reputation system from a technical and an economic perspective. Based on these requirements, we propose a flexible solution that facilitates the incorporation of reputation information into markets of composed services while simultaneously preserving privacy of customers who provide feedback. The requirements we formulate in this paper have just been partially met in literature. An integrated approach, however, has not been addressed yet.}}, author = {{Brangewitz, Sonja and Jungmann, Alexander and Petrlic, Ronald and Platenius, Marie Christin}}, booktitle = {{Proceedings of the 6th International Conferences on Advanced Service Computing (SERVICE COMPUTATION)}}, pages = {{49--57}}, title = {{{Towards a Flexible and Privacy-Preserving Reputation System for Markets of Composed Services}}}, year = {{2014}}, } @techreport{349, abstract = {{Identity-based cryptography has attracted attention in the cryptographic research communityin recent years. Despite the importance of cryptographic schemes for applicationsin business and law, the legal implications of identity-based cryptography have not yetbeen discussed. We investigate how identity-based signatures fit into the legal framework.We focus on the European Signature Directive, but also take the UNCITRAL Model Law onElectronic Signatures into account. In contrast to previous assumptions, identity-basedsignature schemes can, in principle, be used even for qualified electronic signatures,which can replace handwritten signatures in the member states of the European Union.We derive requirements to be taken into account in the development of future identitybasedsignature schemes.}}, author = {{Sorge, Christoph}}, title = {{{The Legal Classification of Identity-Based Signatures}}}, year = {{2014}}, } @inproceedings{355, abstract = {{In the last decade pairings have become an important, and often indispensable, ingredient in the construction of identity-based and attribute-based cryptosystems, as well as group signatures and credential systems. Consequently, the applicability of timing, power, or fault attacks to implementations of pairings is an important research topic. We will review some of the known results in this area.}}, author = {{Blömer, Johannes and Günther, Peter and Liske, Gennadij}}, booktitle = {{Proceedings of Fault Tolerance and Diagnosis in Cryptography(FDTC)}}, pages = {{1----7}}, title = {{{Tampering attacks in pairing-based cryptography}}}, doi = {{10.1109/FDTC.2014.10}}, year = {{2014}}, } @inproceedings{366, abstract = {{On-The-Fly (OTF) Computing constitutes an approach towards highly dynamic and individualized software markets. Based on service-oriented computing, OTF Computing is about realizing global markets of services that can be flexibly combined. We report on our current research activities, the security and privacy implications thereof, and our approaches to tackle the challenges. Furthermore, we discuss how the security and privacy challenges are addressed in research projects similar to OTF Computing.}}, author = {{Petrlic, Ronald and Jungmann, Alexander and Platenius, Marie Christin and Schäfer, Wilhelm and Sorge, Christoph}}, booktitle = {{Tagungsband der 4. Konferenz Software-Technologien und -Prozesse (STeP 2014)}}, pages = {{131--142}}, title = {{{Security and Privacy Challenges in On-The-Fly Computing}}}, year = {{2014}}, }