On the Security of the Lee-Hwang Group-Oriented Undeniable Signature Schemes

• Main Authors: WANG, Guilin, ZHOU, Jianying, DENG, Robert H.
• Format: text
• Language: English
• Published: Institutional Knowledge at Singapore Management University 2004
• Subjects: Information Security
• Online Access: https://ink.library.smu.edu.sg/sis_research/558; https://ink.library.smu.edu.sg/context/sis_research/article/1557/viewcontent/On_the_Security_of_the_Lee_Hwang_Group_Oriented_Un.pdf
• Institution: Singapore Management University

Undeniable signature is an intriguing concept introduced by Chaum and van Antwerpen at Crypto89. In 1999, Lee and Hwang presented two group-oriented undeniable signature schemes with a trusted center. Their schemes are natural generalizations of Chaums zero knowledge undeniable signature scheme proposed in 1990. However, we find that the Lee-Hwang schemes are insecure. In this paper, we demonstrate five effective attacks on their schemes: four of them are insider universal forgeries, in which one dishonest member (maybe colluding 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. We also suggest heuristic improvements to overcome some of the problems involved in these attacks.