关键词: 无证书签名, 公钥替换攻击, 分叉技术, 双线性对

Abstract: Recently，Zhang et al. has proposed an efficient certificateless signature scheme and has given a formal security proof of the scheme.In this paper，it shows that the proposed scheme is insecure against public key replacement attacks，that is，an adversary can forge a valid signature for any message of any user under public key replacement attacks and the attack method is showed in detail.It is also pointed out that there exist fatal proof flaws in its security proof，and the security proof flaws is the adversary must know the secret key of the substituted public key in proving the security by the forking technique of Rafael and Ricardo.It is found that these flaws exist in other literature，and the flaws reasons are analyzed and the improvement measures are put forward.

Key words: certificateless signature, public key replacement attack, forking technique, bilinear pairing