On the Security of a Proxy Ring Signature with Revocable Anonymity

Abstract

As an important delegation technique, proxy signature appears many kinds of different variants. Among of them, the requirements of proxy signer’s privacy protection and anonymous identity revocation are very important in some practical applications. Recently, Wang et al. proposed a new signature type: proxy ring signature with revocable anonymity, which allows that proxy signer anonymously produces a proxy signature. And they claimed that their scheme is insecure. Unfortunately, in this paper, by analyzing their scheme, we show that the scheme does not satisfy anonymity; meanwhile, it cannot also revoke anonymity of proxy signer identity. After we give the corresponding attacks on the scheme and the reasons to produce suck attacks, an improved proxy ring signature with revoking anonymity is proposed. It can resist our attacks.