Security Analysis of an Enhanced Certificateless Signcryption in the Standard Model

Abstract

Quite recently, Luo and Wan putted forward a new certificateless signcryption (CLSC) scheme with low computation cost in the standard model. They stated that their newly proposed scheme achieves the unforgeability against adaptive chosen message attack (i.e, unforgeability) and indistinguishability against adaptive chosen ciphertext attack (i.e., confidentiality). However, we find that the scheme cannot reach the claimed security feature. Specifically, in this paper, we will demonstrate that in Luo and Wan’s CLSC scheme, the plaintext can be easily recovered from the ciphertext by ordinary attacker and malicious-but-passive KGC. In addition, we identify that this scheme even cannot resist forgery attack of a malicious KGC.