A Secure Strong Proxy Signature Scheme with Proxy Signer Privacy Protection

A proxy signature scheme enables an entity to delegate its signing rights to another entity. Since the proxy signature concept was proposed by Mambo et al., many variant schemes have been appeared. In this paper, we propose a new proxy signature scheme with a proxy signer's privacy protection. In proxy signer's privacy scenario, the identity of the proxy signer cannot be revealed in a proxy signature unless the alias authority reveals it. The verifier only knows that the proxy signer is certified by the alias authority. The anonymity of the proxy signer gives an additional application such as electronic voting, electronic cash. In 2002, Shum et al. firstly proposed a scheme. But this scheme was broken because it is based on the LKK proxy signature scheme which is known to be insecure. We modify the triple Schnorr scheme and apply the modified result to our scheme.