Security Issues in Querying Encrypted Data

There has been considerable interest in querying encrypted data, allowing a “secure database server” model where the server does not know data values. This paper shows how results from cryptography prove the impossibility of developing a server that meets cryptographic-style definitions of security and is still efficient enough to be practical. The weaker definitions of security supported by previous secure database server proposals have the potential to reveal significant information. We propose a definition of a secure database server that provides probabilistic security guarantees, and sketch how a practical system meeting the definition could be built and proven secure. The primary goal of this paper is to provide a vision of how research in this area should proceed: efficient encrypted database and query processing with provable security properties.