An improved E-payment protocol based on quantum blind signature without entanglement

E-payment plays an important role in modern daily life, so the security problem of E-payment has been widely concerned by researchers. In a recent paper [Int. J. Theor. Phys. 57, 2657 (2018)], the authors presented a trusted third-party E-payment protocol based on quantum blind signature without entanglement. In this paper, we show that there is a serious security flaw in their E-payment protocol. That is, the partial keys will be disclosed by performing a simple attack strategy. Furthermore, we propose an improved E-payment protocol and analyze its security.