A designated cloud server-based multi-user certificateless public key authenticated encryption with conjunctive keyword search against IKGA

With the massive growth of the World Wide Web (i.e., internet), individual users or companies can store and manage large amounts of sensitive data to outsource it to the cloud server. Despite its advantages, such as reducing local storage, reducing overhead, and providing backups, it faces security and data privacy issues. Many public-key encryption with keyword search (PEKS) schemes are developed to resolve the above problems. Nevertheless, those are not efficiently suitable for multi-user scenario applications. Recently, a new scheme developed called Multi-user certificateless public key encryption with a conjunctive keyword search (mCLPECK) scheme. It contains two features: the multi-user environment and the conjunctive keyword search function. Nevertheless, it requires a secure channel while transmitting the trapdoor to the cloud server, which is not practical in applications, and it cannot resist the keyword guessing attack (KGA). We propose a primitive called a designated cloud server-based multi-user certificateless public key authenticated encryption with conjunctive keyword search (dmCLPAECKS) scheme. It doesn't require a secure channel between the designated cloud server and a data receiver and provides security against keyword guessing attack (KGA) in random oracle model. Furthermore, our proposed scheme shows better results than other related schemes in terms of communication and computation cost.