Cryptanalysis of an identity-based convertible undeniable signature scheme

Abstract

In this paper, we cryptanalyze an identity-based convertible undeniable signature scheme which claimed to be secure under the random oracle model. Our result shows that the signature leaks information on signer identity and fails to provide both invisibility and anonymity under the known message attack. We propose a fix for the vulnerability by removing some information from the signature with the need for the signer to keep the record of every signed message.