An efficient t-times proxy ring signature scheme with revocable anonymity

Proxy signature is an important delegation technique. Since it was introduced in 1996, many variants of proxy signature schemes have been proposed. Among of them, the requirement of proxy signer´s privacy protection and the revocation of proxy signer´s anonymous identity are needful in some practical applications. To satisfy special occasion demand, a new signature type: proxy ring signature with revocable anonymity, was proposed by Hu et al. It allows that proxy signer anonymously produce a proxy signature. However, until now, all proxy ring signature schemes with revocable anonymity are insecure, they cannot realize anonymity revocation. In some cases, signing time of proxy signer needs to be restricted and the illegal behavior of proxy signer needs to be revoked. To overcome this problem, we propose a t ¡times proxy ring signature with revocable anonymity in the paper, it can not only realize anonymity revocation, but also limit signing times of proxy signer. Finally, we show that the proposed scheme is completeness, anonymity, revocation and unforgeability.