Abstract: To overcome the drawbacks， such as high computational complexity and heavy communication， in the present threshold proxy signature schemes， a nonrepudiable threshold proxy signature scheme was proposed. To improve the security，when a signer applies for public key certificate to the CA， the CA validates the signer′s private key associated with the signer′s public key by the method of zero-knowledge proof. To improve the efficiency， in the phase of proxy key generation， original signer only needs to calculate and broadcast a public proxy share to the proxy group， and the group members generate their own proxy keys concurrently. Comparing with the schemes that original signer generates proxy keys one by one for all the proxy members， the amount of calculation was greatly reduced by the proposed method. The security model of three types of adversaries was proposed. It was simulated that the adversaries forge the signature. The new scheme was proved to be secure by the simulation process.

Key words: cryptography, proxy signature, threshold proxy signature, zero-knowledge proof, adversary