Revisiting frequency-smoothing encryption: new security definitions and efficient construction

Deterministic encryption (DET) allows for fast retrieval of encrypted information, but it would cause significant leakage of frequency information of the underlying data, which results in an array of inference attacks. Simply replacing DET with fully randomized encryption is often undesirable in the scenario of an encrypted database since it incurs a large overhead in query and storage. Frequency Smoothing Encryption (FSE) is a practical encryption scheme to protect frequency information. Current FSE constructions still fall short of efficiency and a reasonable security definition. We revisit FSE and propose two security definitions from both theoretical and practical perspectives. Furthermore, we adopt a novel partitioning strategy to construct a new FSE scheme to improve performance. Experimental results show that compared with others, our scheme achieves excellent query performance while attaining security against inference attacks.