Privacy preserving document indexing infrastructure for a distributed environment

To carry out work assignments, small groups distributed within a larger enterprise or collaborative community often need to share documents among themselves while shielding those documents from others' eyes. In this situation, users need an indexing facility that can quickly locate relevant documents that they are allowed to access, without (1) leaking information about the remaining documents, (2) imposing a large management burden as users, groups, and documents evolve, or (3) requiring users to agree on a central completely trusted authority. In order to achieve this aim user access levels and access control have to be reflected in the index structures and/or retrieval algorithms as well as in ranking the search results. My Ph.D. work focuses on building up an indexing infrastructure which supports confidential indexing, sharing and retrieval of unstructured information which is spread over a number of distributed access-controlled collections. In order to allow for effective and efficient indexing and retrieval in these settings, it considers aspects of confidentiality preservation within an outsourced inverted index, a DHT index structure in P2P networks as well as confidential top-k information retrieval.