Improvement on Q. Xie threshold proxy signature scheme against collusion attack

In a (t, n) threshold proxy signature scheme, the original signer can delegate the signing power to n proxy signers such that any t or more out of n proxy signers can sign messages on behalf of the original signer, but t - 1 or less of the proxy signers cannot generate a proxy signature. In this paper, we will improve the security of Xie´s threshold proxy signature scheme against the new types of collusion attack was presented by Liu and Tan in 2007 We also present that our improved scheme is more efficient than Xie´s scheme in terms of computational complexities.