On the Security of a Certificateless Signature Scheme

Abstract

Certificateless public key cryptography eliminates inherent key escrow problem in identity-based cryptography, and does not yet requires certificates as in the traditional public key infrastructure. Recently, Yu et al. propose a new certificateless signature scheme and their scheme offers shorter system parameters and higher computational efficiency than the previous schemes in the standard model. However, in this paper, we show Yu et al.'s certificateless signature scheme is vulnerable to malicious-but-passive KGC attack where a malicious KGC can forge valid signatures by embedding extra trapdoors in the system parameter.

Efficient and secure certificateless signature scheme in the standard model

“…From the method, our scheme can resist the attack of Xiong et al [20]. Second, we embed part of public key into the signature, which is a good method to withstand the attack of malicious-but-passive KGC proposed by Cheng et al [24]. Finally, our scheme bind the signer's public key to his PSK and identity ID which can promote our scheme from trust level 2 to level 3 by the definition of Girault [25].…”

“…But they put all the focus on the public-key-replace attack proposed by Xia et al [22]. And, it has been proved insecure under the attack by Cheng et al [24]. Besides, Yu et al [23] ignored that a KGC can embed trapdoor information into the system public parameters to create valid signature.…”