On the Interoperability of Encrypted Databases

Encrypted database is an emerging and promising technology that is able to run SQL operations on encrypted data. However, most existing encrypted databases have no data interoperability, i.e., the output of an operator (e.g., addition) cannot be taken as input of another (e.g., comparison). As a result, these encrypted databases can only support simple queries like addition, multiplication and comparison, but unable to support a composition of these simple queries (e.g., SELECT user id FROM salary WHERE V1 + V2 > 5000). In SIGMOD '14, Wong et al. propose SDB, which to the best of our knowledge is the only encrypted database that achieves data interoperability. Unfortunately, it has recently been broken (VLDB '21). In this paper, we propose a novel encrypted database named SDB+. It achieves data interoperability based on a suit of sophisticated designs. We formally prove that SDB+ achieves indistinguishability under chosen query attacks (IND-CQA). We provide a full-fledged implementation and run it on three benchmarks. Our experimental results show that SDB+ achieves comparable efficiency with SDB, even though the latter is insecure.