Database Fragmentation with Confidentiality Constraints: A Graph Search Approach

Database fragmentation is a promising approach that can be used in combination with encryption to achieve secure data outsourcing which allows clients to securely outsource their data to remote untrusted server(s) while enabling query support using the outsourced data. Given a set of confidentiality constraints, it vertically partitions the database into fragments such that the set of attributes in each constraint do not appear together in any one fragment. The optimal fragmentation problem is to find a fragmentation with minimum cost for query support. In this paper, we propose an efficient graph search based approach which obtains near optimal fragmentation. We model the fragmentation search space as a graph and propose efficient search algorithms on the graph. We present static and dynamic search strategies as well as a novel level-wise graph expansion technique which dramatically reduces the search time. Extensive experiments showed that our method significantly outperforms other state-of-the-art methods.