Designated tester certificateless encryption with keyword search

In this paper, we introduce the notion of designated tester certificateless encryption with keyword search (dCLEKS) and define the required security model. In the defined security model, in addition to the security of ciphertexts, we consider the security of trapdoors through which the security against offline keyword guessing attack (oKGA) is ensured. We further propose a concrete dCLEKS scheme and show that it is secure in the defined security model under the intractability of GBDH and CDH problems. To the best of our knowledge, the proposed dCLEKS scheme is the only secure searchable certificateless encryption scheme that provides security against oKGA performed by outside attackers and does not require secure channels for transmission of ciphertexts and trapdoors between users and the server.