Hidden policy ciphertext-policy attribute based encryption with conjunctive keyword search

Attribute-based encryption with keyword search (ABKS) enables data owners to delegate the keyword search ability to other users complying with the specified access control policy. However, most existing ABKS schemes cannot guarantee the privacy of the access structures, which may contain sensitive information. Furthermore, current ABKS schemes are designed for single-keyword searches, which may affect the user's experience in practical application. To solve these problems, we propose a novel primitive named hidden policy ciphertext-policy attribute based encryption with conjunctive keyword search (HP-CPABCK). In addition to supporting conjunctive keyword search, HP-CPABCK makes the data user learn nothing about the access structure if his/her attribute cannot satisfy the access control policy specified by the data owner. Moreover, the data owner designates a server to perform the test operation in HP-CPABCK to resist off-line keyword guessing attacks. We formulate a security model for the proposed HP-CPABCK scheme, and show its security in the standard model. Finally, the performance evaluation demonstrate the applicability of our scheme.