Analysis on a Non-repudiable Threshold Proxy Signature Scheme with Known Signers

摘要

In 2000, Hwang et al. made an improvement on Sun's threshold proxy signature scheme. In 2004, Tzeng et al. present that Hwang et al.'s scheme is vulnerable against attack. A malicious original signer can forge the threshold proxy signatures without the agreement of the proxy signers. Tzeng et al. also constructed a nonrepudiable threshold proxy signature scheme with known signers and claimed the proposed scheme improved the security of Hwang et al.'s scheme. In this paper, we pointed that reasoning in THY-scheme exist severity error. Since it is repaired hardly possible that this reasoning in secret share generation phase of THY-scheme existed error, therefore THY-scheme is not useful even though changed some formulae.