CFB-DSSE: Efficient Secure Dynamic Searchable Encryption Scheme with Conjunctive Search for Smart Healthcare

Smart healthcare provides more convenient services to patients and medical institutions. However, it also suffers from medical data privacy leakage and broad query results. Although many dynamic symmetric searchable encryption (DSSE) schemes solve these problems, they still suffer from forward and backward security, the absence of non-interactive queries, and large computational and communication overhead for conjunctive queries. To address these issues, we propose a conjunctive forward-backward secure dynamic symmetric searchable encryption scheme for smart healthcare called CFB-DSSE. First, we utilize inner product predicate encryption technology to achieve conjunctive queries while preserving user privacy. Second, we employ tailored proxy re-encryption technology to ensure forward and backward security, thereby enhancing smart healthcare system security. Third, we design a double-layer encrypted bitmap index structure to replace the traditional homomorphic encryption technology to encrypt the bitmap index, reducing computational and communication overhead and enabling non-interactive queries. Through experiments and analysis, CFB-DSSE scheme demonstrates considerable advancements in protecting medical data privacy and improving query efficiency. CFB-DSSE can save at least 100ms of search time compared to other related schemes.