In Eurocrypt 2005, Kurosawa and Heng proposed a set of 3-move witness indistinguishable protocols to be incorporated in the confirmation and disavowal protocols of the FDH variant of undeniable signature schemes. Their 3-move protocols gave rise to the development of many other variants of undeniable signature schemes. In 2010, Zhou, Zhang and Li showed a weakness in Kurosawa and Heng's proof system which enables a malicious prover to impersonate the signer. Libert and Quisquater proposed the first identity-based undeniable signature scheme. In 2007, Li et al. proposed a universal forgery attack on their scheme. In this paper, we show that both of the attacks which were proposed on Kurosawa and Heng's proof system and Libert and Quisquater's scheme have fatal errors, and therefore, both claims are false.
['Rouzbeh Behnia', 'Swee-Huay Heng']
Notes on Two Flawed Attacks on Undeniable Signature Schemes