On Zhang et al.’s Convertible Limited Verifier Signature Scheme

Recently,Zhang et al.proposed a convertible limited verifier signature scheme and claimed that only the limited verifier can independently convert the signature into an ordinary one.In this paper,we show that,in Zhang et al.’s scheme,the signer not only can confirm or deny the signature,but also can independently convert the given signature into publicly verifiable one,and Zhang et al.’s claim is hence incorrect.