@article{10790, author = {{Blömer, Johannes and Brauer, Sascha and Bujna, Kathrin and Kuntze, Daniel}}, issn = {{1862-5347}}, journal = {{Advances in Data Analysis and Classification}}, pages = {{147–173}}, title = {{{How well do SEM algorithms imitate EM algorithms? A non-asymptotic analysis for mixture models}}}, doi = {{10.1007/s11634-019-00366-7}}, volume = {{14}}, year = {{2020}}, } @phdthesis{15482, author = {{Löken, Nils}}, title = {{{Cryptography for the Crowd — A Study of Cryptographic Schemes with Applications to Crowd Work}}}, doi = {{10.17619/UNIPB/1-854}}, year = {{2020}}, } @misc{18638, author = {{Kramer, Paul}}, publisher = {{Universität Paderborn}}, title = {{{Comparison of Zero-Knowledge Range Proofs}}}, year = {{2020}}, } @article{2916, author = {{Brauer, Sascha}}, issn = {{0304-3975}}, journal = {{Theoretical Computer Science}}, pages = {{88--106}}, publisher = {{Elsevier}}, title = {{{Complexity of single-swap heuristics for metric facility location and related problems}}}, doi = {{10.1016/j.tcs.2018.04.048}}, volume = {{754}}, year = {{2019}}, } @misc{15746, author = {{Otte, Oliver}}, title = {{{Outsourced Decryption of Attribute-based Ciphertexts}}}, year = {{2019}}, } @misc{15747, author = {{Wördenweber, Nico Christof}}, title = {{{On the Security of the Rouselakis-Waters Ciphertext-Policy Attribute-Based Encryption Scheme in the Random Oracle Model}}}, year = {{2019}}, } @misc{15819, author = {{Leutnant, Matthias}}, title = {{{Experimentelle Untersuchung des SEM-Algorithmus}}}, year = {{2019}}, } @misc{13128, author = {{Bröcher, Henrik}}, publisher = {{Universität Paderborn}}, title = {{{Rational Secure Multiparty Computation}}}, year = {{2019}}, } @misc{10306, author = {{Porzenheim, Laurens Alexander}}, title = {{{Post-Quantum Secure Group Signatures}}}, year = {{2019}}, } @inproceedings{13554, abstract = {{We propose a novel personal reputation system for cross-platform reputation. We observe that, in certain usage scenarios, e.g. crowd work, the rater anonymity property typically imposed on reputation systems is not necessary. Instead, we propose a relaxed notion of rater anonymity that is more applicable in the crowd work scenario. This allows us to construct a secure personal reputation system from simple cryptographic primitives.}}, author = {{Blömer, Johannes and Löken, Nils}}, booktitle = {{Security and Trust Management, STM 2019}}, title = {{{Personal Cross-Platform Reputation}}}, doi = {{10.1007/978-3-030-31511-5_9}}, volume = {{11738}}, year = {{2019}}, } @inproceedings{13557, abstract = {{We present a searchable encryption scheme for dynamic document collections in a multi-user scenario. Our scheme features fine-grained access control to search results, as well as access control to operations such as adding documents to the document collection, or changing individual documents. The scheme features verifiability of search results. Our scheme also satisfies the forward privacy notion crucial for the security of dynamic searchable encryption schemes.}}, author = {{Blömer, Johannes and Löken, Nils}}, booktitle = {{12th International Symposium on Foundations and Practice of Security, FPS 2019}}, publisher = {{Springer}}, title = {{{Dynamic Searchable Encryption with Access Control}}}, volume = {{12056}}, year = {{2019}}, } @misc{13592, author = {{Pilot, Matthias}}, publisher = {{Universität Paderborn}}, title = {{{Efficient Finite-Field Arithmetic for Elliptic Curve Cryptography in Java}}}, year = {{2019}}, } @misc{13648, author = {{Scholz, Swante}}, publisher = {{Universität Paderborn}}, title = {{{Implementation and Comparison of Elliptic Curve Algorithms in Java}}}, year = {{2019}}, } @phdthesis{13679, author = {{Brauer, Sascha}}, title = {{{Classification and Approximation of Geometric Location Problems}}}, doi = {{10.17619/UNIPB/1-816}}, year = {{2019}}, } @inproceedings{13904, abstract = {{In this paper, we introduce updatable anonymous credential systems (UACS) and use them to construct a new privacy-preserving incentive system. In a UACS, a user holding a credential certifying some attributes can interact with the corresponding issuer to update his attributes. During this, the issuer knows which update function is run, but does not learn the user's previous attributes. Hence the update process preserves anonymity of the user. One example for a class of update functions are additive updates of integer attributes, where the issuer increments an unknown integer attribute value v by some known value k. This kind of update is motivated by an application of UACS to incentive systems. Users in an incentive system can anonymously accumulate points, e.g. in a shop at checkout, and spend them later, e.g. for a discount.}}, author = {{Blömer, Johannes and Bobolz, Jan and Diemert, Denis Pascal and Eidens, Fabian}}, booktitle = {{Proceedings of the 2019 ACM SIGSAC Conference on Computer and Communications Security - CCS '19}}, location = {{London}}, title = {{{Updatable Anonymous Credentials and Applications to Incentive Systems}}}, doi = {{10.1145/3319535.3354223}}, year = {{2019}}, } @inproceedings{2862, author = {{Blömer, Johannes and Eidens, Fabian and Juhnke, Jakob}}, booktitle = {{Topics in Cryptology - {CT-RSA} 2018 - The Cryptographers' Track at the {RSA} Conference 2018, Proceedings}}, isbn = {{9783319769523}}, issn = {{0302-9743}}, location = {{San Francisco, CA, USA}}, pages = {{470--490}}, publisher = {{Springer International Publishing}}, title = {{{Practical, Anonymous, and Publicly Linkable Universally-Composable Reputation Systems}}}, doi = {{10.1007/978-3-319-76953-0_25}}, year = {{2018}}, } @article{2685, author = {{Blömer, Johannes and Kohn, Kathlén}}, issn = {{2470-6566}}, journal = {{SIAM Journal on Applied Algebra and Geometry.}}, number = {{2}}, pages = {{314--338}}, title = {{{Voronoi Cells of Lattices with Respect to Arbitrary Norms}}}, doi = {{10.1137/17M1132045}}, volume = {{2}}, year = {{2018}}, } @inproceedings{3265, abstract = {{We present CLARC (Cryptographic Library for Anonymous Reputation and Credentials), an anonymous credentials system (ACS) combined with an anonymous reputation system. Using CLARC, users can receive attribute-based credentials from issuers. They can efficiently prove that their credentials satisfy complex (access) policies in a privacy-preserving way. This implements anonymous access control with complex policies. Furthermore, CLARC is the first ACS that is combined with an anonymous reputation system where users can anonymously rate services. A user who gets access to a service via a credential, also anonymously receives a review token to rate the service. If a user creates more than a single rating, this can be detected by anyone, preventing users from spamming ratings to sway public opinion. To evaluate feasibility of our construction, we present an open-source prototype implementation.}}, author = {{Bemmann, Kai and Blömer, Johannes and Bobolz, Jan and Bröcher, Henrik and Diemert, Denis Pascal and Eidens, Fabian and Eilers, Lukas and Haltermann, Jan Frederik and Juhnke, Jakob and Otour, Burhan and Porzenheim, Laurens Alexander and Pukrop, Simon and Schilling, Erik and Schlichtig, Michael and Stienemeier, Marcel}}, booktitle = {{Proceedings of the 13th International Conference on Availability, Reliability and Security - ARES '18}}, isbn = {{978-1-4503-6448-5}}, location = {{Hamburg, Germany}}, publisher = {{ACM}}, title = {{{Fully-Featured Anonymous Credentials with Reputation System}}}, doi = {{10.1145/3230833.3234517}}, year = {{2018}}, } @inproceedings{2965, author = {{Blömer, Johannes and Löken, Nils}}, booktitle = {{Proceedings of the 13th International Conference on Availability, Reliability and Security, ARES 2018}}, isbn = {{978-1-4503-6448-5}}, location = {{Hamburg, Germany}}, pages = {{25:1----25:10}}, publisher = {{ACM}}, title = {{{Cloud Architectures for Searchable Encryption}}}, doi = {{10.1145/3230833.3230853}}, year = {{2018}}, } @techreport{5820, abstract = {{In this paper, we investigate the use of trusted execution environments (TEEs, such as Intel's SGX) for an anonymous communication infrastructure over untrusted networks. For this, we present the general idea of exploiting trusted execution environments for the purpose of anonymous communication, including a continuous-time security framework that models strong anonymity guarantees in the presence of an adversary that observes all network traffic and can adaptively corrupt a constant fraction of participating nodes. In our framework, a participating node can generate a number of unlinkable pseudonyms. Messages are sent from and to pseudonyms, allowing both senders and receivers of messages to remain anonymous. We introduce a concrete construction, which shows viability of our TEE-based approach to anonymous communication. The construction draws from techniques from cryptography and overlay networks. Our techniques are very general and can be used as a basis for future constructions with similar goals.}}, author = {{Blömer, Johannes and Bobolz, Jan and Scheideler, Christian and Setzer, Alexander}}, title = {{{Provably Anonymous Communication Based on Trusted Execution Environments}}}, year = {{2018}}, }