Cryptology ePrint Archive: Report 2002/150

Cryptanalysis of the Lee-Hwang Group-Oriented Undeniable Signature Schemes

Guilin Wang, Jianying Zhou, and Robert H. Deng

Abstract: Undeniable signature is an intriguing concept introduced by Chaum and Antwerpen at Crypto'89. In 1999, Lee and Hwang presented two group-oriented undeniable signature schemes with a trusted center. Their schemes are natural generalizations of Chaum's zero-knowledge undeniable signature scheme proposed in 1990. However, we find that the Lee-Hwang schemes are insecure. In this paper, we demonstrate five attacks on their schemes: four of them are universal forgery, in which one dishonest member (maybe collude with a verifier) can get a valid signature on any chosen massage, and another attack allows a dishonest member to prevent honest members from generating valid signatures but his cheating behavior is undetected. We also suggest heuristic improvements to overcome some of the problems involved in these attacks.

Category / Keywords: public-key cryptography / digital signatures, undeniable signatures, cryptanalysis

Publication Info: Technical Report

Date: received 29 Sep 2002

Contact author: glwang at lit a-star edu sg

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation

Version: 20021001:194252 (All versions of this report)

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