Cryptanalysis of Nonrepudiable Threshold Proxy Signature Schemes with Known Signers

Article type: Research Article

Authors: Hwang, Shin‐Jia | Chen, Chiu‐Chin

Affiliations: Department of Computer Science and Information Engineering, TamKang University, Tamsui, Taipei Hsien, 251, Taiwan, ROC, e‐mail: sjhwang@mail.tku.edu.tw | Department of Information Management, Chaoyang University of Technology, Wufeng, Taichung Country, 413, Taiwan, ROC, e‐mail: s8914604@mail.cyut.edu.tw

Abstract: Sun's nonrepudiation threshold proxy signature scheme is not secure against the collusion attack. In order to guard against the attack, Hwang et al. proposed another threshold proxy signature scheme. However, a new attack is proposed to work on both Hwang et al.'s and Sun's schemes. By executing this attack, one proxy signer and the original signer can forge any valid proxy signature. Therefore, both Hwang et al.'s scheme and Sun's scheme were insecure.

Keywords: digital signature, proxy signature, threshold proxy signature

Journal: Informatica, vol. 14, no. 2, pp. 205-212, 2003