Abstract: Many proxy signature schemes have the defect that they cannot solve the proxy revocation problem. Based on the bilinear pairings, a new proxy signature scheme is proposed in this paper. Motivated by the idea of(2, 2) threshold, a security mediator (SEM) is introduced in our scheme to (1) help a proxy signer to generate valid proxy signatures, (2) examine whether a proxy signer signs according to the warrant, and (3) check the revocation of a proxy signer. It is shown that the proposed scheme satisfies all the security requirements for a secure proxy signature. Moreover, a proxy signer must cooperate with the SEM to generate a valid proxy signature, which makes the new scheme have an effective and fast proxy revocation.

Key words: proxy signature, security mediator, proxy revocation