Cryptanalysis of Lee-Hwang-Yang blind signature scheme

In 2005, Lee et al. proposed a blind signature scheme based on the discrete-logarithm problem to achieve the untraceability or unlinkability property. However, the scheme will be demonstrated as not being secure in this manuscript. We design an attack on the scheme such that a signature requester can obtain more than one valid signatures by performing only one round of the protocol. It violates an important security requirement of blind signatures.