Many smart card-based remote authentication schemes have been proposed, due to its convenience and secure computation of the smart card. However, these schemes didn?t protect the users? identities while authenticating the users, even though user anonymity is an important issue in many e-commerce applications. In 2004, Das et al. proposed a remote authentication scheme to authenticate users while preserving the users? anonymity. Their scheme adopted dynamic identification to achieve this function. This article points out Das et al.?s scheme fails to protect the user?s anonymity, and propose a new scheme to conquer the weakness.