Abstract：This article discussed an authentication scheme recently advanced by Yuan Ding et al, and indicated that the scheme was vulnerable to dictionary attack, man-in-the-middle attack and denial-of-service attack to the server. And then a dynamic authentication scheme using smart card was proposed and analyzed. The analysis shows that the proposed new scheme, which provides mutual authentication, has the properties of high security and low computational cost, and that it supplies secure, friendly and convenient password-change phase and the server of the scheme does not need to maintain the verification tables used to help authentication.
