Query recovery attacks on searchable encryption based on partial knowledge

While Searchable Encryption (SE) is often used to support securely outsourcing sensitive data, many existing SE solutions usually expose certain information to facilitate better performance, which often leak sensitive information, e.g., search patterns are leaked due to observable query trapdoors. Several inference attacks have been designed to exploit such leakage, e.g., a query recovery attack can invert opaque query trapdoors to their corresponding keywords. However, most of these existing query recovery attacks assume that an adversary knows almost all plaintexts as prior knowledge in order to successfully map query trapdoors to plaintext keywords with a high probability. Such an assumption is usually impractical. In this paper, we propose new query recovery attacks in which an adversary only needs to have partial knowledge of the original plaintexts. We further develop a countermeasure to mitigate inference attacks on SE. Our experimental results demonstrate the feasibility and efficacy of our proposed scheme.