Information Sharing Across Private Databases: Secure Union and Intersection Revisited

There is a growing demand for sharing information across multiple autonomous and private databases. The problem is usually formulated as a secure multiparty computation problem where a set of parties wish to jointly compute a function of their private inputs such that the parties learn only the result of the function but nothing else. In this paper we analyze existing and potential solutions for secure multiparty computation protocols for union and intersection. We also present an alternative random shares based approach and show that the protocols, although quite simple, are more efficient than existing protocols while providing reasonable level of security that can be adjusted by users. We formally analyze the security properties and the cost of our protocols. We also experimentally compare the performance of our approach with the existing solutions.