Towards efficient verifiable conjunctive keyword search for large encrypted database

Searchable Symmetric Encryption (SSE) enables a client to securely outsource large encrypted database to a server while supporting efficient keyword search. Most of the existing works are designed against the honest-but-curious server. That is, the server will be curious but execute the protocol in an honest manner. Recently, some researchers presented various verifiable SSE schemes that can resist to the malicious server, where the server may not honestly perform all the query operations. However, they either only considered single-keyword search or cannot handle very large database. To address this challenge, we propose a new verifiable conjunctive keyword search scheme by leveraging accumulator. Our proposed scheme can not only ensure verifiability of search result even if an empty set is returned but also support efficient conjunctive keyword search with sublinear overhead. Besides, the verification cost of our construction is independent of the size of search result. In addition, we introduce a sample check method for verifying the completeness of search result with a high probability, which can significantly reduce the computation cost on the client side. Security and efficiency evaluation demonstrate that the proposed scheme not only can achieve high security goals but also has a comparable performance.