Our research areas cover cryptography and cluster analysis.
Increasingly, people and companies are unable to perform computations on sensitive data on their own. Therefore, they often depend on external service providers, which collect more than the necessary data in this process, for example for advertising and analysis purposes. Using cryptographic methods, it is possible to replace these service providers with decentralized systems that give the user back control over the disclosed data. Our research interests in the field of such secure decentralized systems range from special cases such as incentive systems and anonymous credential systems, over generic secure multi-party computation, to exploring new rational attacker models.
Another research focus is lattice-based cryptography. Here, cryptographic systems are built under the assumption that certain problems based on the mathematical constructs of lattices cannot be solved efficiently. Unlike assumptions about RSA and discrete logarithms, it is assumed that powerful quantum computers cannot solve these lattice-based problems efficiently. Therefore, this field is also referred to as post-quantum cryptography. Based on lattices, we explore constructions such as homomorphic signatures and reputation systems.
The group's other focus area is cluster analysis. The goal of a clustering is to divide some set of objects into groups, the so-called clusters, such that objects in the same cluster are more similar to each other than to objects in other clusters. Nowadays, clustering is ubiquitous in many research areas, such as data mining, image and video analysis, information retrieval, and bioinformatics. Our research focuses on analysing clustering algorithms used in practice and the developement of algorithms with provable approximation bounds.