Further Cryptanalysis of a Signature Scheme with Message Recovery

Chang et al. proposed a new digital signature scheme with message recovery. They claimed that their scheme was accomplished without using one-way hash functions and message redundancy. However, several forgery attacks demonstrated that Chang et al.´s signature scheme with message recovery is not secure. However, the idea of how to get the attacks is unclear. In this paper, we present more general forgery attacks to show clearly how to obtain the attacks. Interestingly, our general forgery covers all the known attacks.