New nonrepudiable threshold proxy signature scheme with known signers

Based on Kim et al.'s threshold proxy signature scheme, Sun proposed an nonrepudiable threshold proxy signature scheme with known signers. In Sun's scheme, actual proxy signers cannot deny the signatures they have signed. However, his scheme is vulnerable against the conspiracy attack. Any t malicious proxy signers can collusively derive the secret keys of other proxy signers and impersonate some other proxy signers to generate proxy signatures. In this paper, we proposed a new nonrepudiable threshold proxy signature scheme that overcomes the above weakness. Furthermore, the proposed scheme is more efficient than Sun's in terms of computational complexities and communication costs.