Certificateless public key encryption with conjunctive keyword search and its application to cloud-based reliable smart grid system

A public key encryption scheme with conjunctive keyword search allows a semi-trusted third party (or a cloud server) to search over an encrypted data after receiving a trapdoor generated from a conjunctive keyword set. Assume that a sender sends a number of data to a receiver and those data are all stored in the same cloud server. Normally, if the receiver uses one keyword or separate keywords to look for through hundreds of data, it might get in return a huge number of associated data and most of them are unwanted. In this paper, we design a new certificateless public key encryption scheme with conjunctive keyword search, which only returns the desired data. We also prove that the designed scheme is secure against adaptive chosen keyword attacks in the random oracle model under bilinear Diffie-Hellman (BDH) problem assumption. Experimental results show that our scheme has better performance during the testing phase and has a lower communication cost than two related schemes. The comparison about security properties also shows that our scheme is more secure than them. Finally, we give an application example of our scheme in a cloud-based reliable smart grid system.