New certificateless public key encryption secure against malicious KGC attacks in the standard model

Abstract

It is an interesting and challenging task to design an efficient certificateless encryption (CLE) scheme whose security can be proved without using random oracles. Although some CLE schemes claimed secure in the standard model have been available in the literature, we find most of the concrete constructions are in fact insecure. In this paper, we first demonstrate the insecurity of the CLE scheme introduced by Hwang and Liu in 2008. We show how a type II adversary breaks the indistinguishability of ciphertexts under chosen ciphertext attacks. We then propose a new concrete CLE scheme. Our new scheme can resist public key replacement attacks as well as malicious key generation center (KGC) attacks. We rigorously prove the security of our construction under the Decisional Bilinear Diffie-Hellman assumption in the standard model.