An Efficient Conjunctive Keyword Searchable Encryption Scheme

In storage service, searchable encryption scheme allows users to access their cipher data selectively, and meanwhile ensures the confidentiality of search data. Since possessing higher search accuracy, conjunctive keyword (namely Boolean combination of multiple keywords) searchable encryption scheme enjoys greater significance in secure storage service application. However, there are some flaws in existing searchable encryption schemes, such as the size of the trapdoor of conjunctive keyword is too large, the search efficiency is slow and there is no support for multiple users search, etc. In this paper, an efficient conjunctive keyword searchable encryption scheme is proposed based on the method that the keywords are encrypted by authorized users and storage server successively，in which authorized users are allowed to search encrypted documents with the trapdoor generated by conjunctive keyword. The scheme is provable secure in the decisional Diffie-Hellman assumption. Compared with the existing schemes, the overall efficiency of the proposed scheme in computation and communication cost, including the size of trapdoor, the speed of keyword encryption and searching, is improved. Moreover, the proposed scheme also supports multiple users, that is, users can be added or revoked dynamically, by this way, and users can share data directly in storage server.