Comments on Islam Et Al.'s Certificateless Designated Server Based Public Key Encryption with Keyword Search Scheme

摘要

Recently, Islam et al. proposed a certificateless designated server based public key encryption with keyword search (CL-dPEKS) scheme which combines the concepts of dPEKS and certificateless public key cryptosystem. In this paper, we show that their scheme does not provide the ciphertext and the trapdoor indistinguishabilities, two important security notions of dPEKS. Concretely, we demonstrate that their CL-dPEKS scheme suffered from off-line keyword guessing attacks on ciphertext and trapdoor by outside adversary and malicious server.