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Journal of Information Science and Engineering, Vol. 25 No. 2, pp. 619-631 (March 2009)

Cryptanalysis and Improvement on a Threshold Proxy Signature Scheme*

Zuo-Wen Tan1,2 and Zhuo-Jun Liu3
 1College of Information Management
Jiangxi University of Finance and Economics
Nanchang, Jiangxi Province 330013, P.R. China
2State Key Laboratory of Information Security
Institute of Software of CAS
Beijing 100190, P.R. China
3KLMM, AMSS of Chinese Academy of Sciences
Beijing 100190, P.R. China

In a (t, n) threshold proxy signature scheme, an original signer can delegate the signature authority to a proxy group of n member such that t or more than t proxy signers can cooperatively sign messages on behalf of the original signer, but t - 1 or fewer proxy signers cannot generate a valid proxy signature. In this paper, we review the security of C. L. Hsu et al.'s threshold proxy signature schemes with known signers. We show that the threshold proxy signature scheme is insecure against forgery attack. C. L. Hsu et al.'s threshold proxy signature scheme is universally forgeable. A new improvement scheme is proposed. The new scheme remedies its weakness. Our proposed threshold proxy signature is secure against chosen message attacks and chosen warrant attacks in the random oracle model under DL assumption.

Keywords: proxy signature, threshold signature, forgery attack, universally forgeable, random oracle model, DL assumption

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Received May 16, 2007; revised September 13, 2007; accepted June 12, 2008.
Communicated by Tzong-Chen Wu.
* This paper was partially supported by Science Research Fund of Jiangxi Province Education Department (No.273), the National Natural Science Foundation of China (No.10701040) and National Key Technology R&D Program (No. 2006BAJ05A01).