A lightweight secure conjunctive keyword search scheme in hybrid cloud

Keyword search over encrypted sensitive data is an essential technique in cloud computing. Many traditional secure retrieval schemes of the encrypted data mainly apply to single file-owner and single retrieval-party scenario, which cannot be used in cloud environment effectively. The emergence of Attribute-Based Encryption (ABE) provides a new solution to deliver secure and multi-parties keyword search over the encrypted data. However, most existing attribute-based keyword search schemes suffer problems, such as, imposed heavy computational burden for file-owner, limited expressive capability of access control policy, supported for single keyword search only, etc. Hence, we present a Lightweight secure Conjunctive Keyword Search scheme in hybrid cloud environment (LCKS) based on ciphertext-policy ABE algorithm, which supports file-owner authorized conjunctive keyword search for multi-parties. By delegating most computational tasks to private cloud servers, LCKS enables file-owners to generate keyword index efficiently while delivering a fine-grained access control policy through adopting an expressive tree structure. Both security analysis and performance evaluation show that LCKS is secure, highly efficient, and well suited for hybrid cloud.