Comment on 'Efficient and secure dynamic ID-based remote user authentication scheme for distributed systems using smart cards'

This comment paper refers to an article published by Leu and Hsieh in IET Information Security in the year 2014. Leu and Hsieh proposed a remote user authentication protocol for distributed systems using smartcard. Their protocol affords user anonymity and no verification tables at either end, which can decrease the storage space along with the computations. Their protocol can resist security attacks and is efficient compared with few relevant protocols in terms of computational cost. However, this comment paper brings questions about the correctness of the design of Leu and Hsieh's protocol.