中文摘要：

2000年，Hwang和Li提出了一个新的智能卡远程用户认证方案，随后Chan和Cheng对该方案进行了成功的攻击．最近Shen，Lin和Hwang针对该方案提出了一种不同的攻击方法，并提供了一个改进方案用于抵御这些攻击．2003年，Leung等认为Shen-Lin-Hwang改进方案仍然不能抵御Chan和Cheng的攻击，他们用改进后的Chang—Hwang攻击方法进行了攻击．文中主要在Hwang—Li方案的基础上，提出了一个新的远程用户认证方案，该方案主要在注册阶段和登录阶段加强了安全性，抵御了类似Chan—Cheng和Chang—Hwang的攻击．

英文摘要：

In 2000, Hwang and Li proposed a new remote user authentication scheme using smart cards. Chan and Cheng showed that the masquerade attack is successful on this scheme. Recently Shen, Lin and Hwang pointed out a different type of attack on this scheme and presented a modified scheme to remove these defects. Further in 2003, Leung, et al. showed that this modified scheme is still vulnerable to the attack proposed by Chan and Cheng. In addition, they showed that the extended attack proposed by Chang and Hwang also works well. In this paper we present a new remote user authentication scheme which is a modified form of Hwang-Li＇s scheme. The scheme can withstand attack that similar to Chan and Cheng＇attack and Chang and Hwang＇ attack in registration phase and authentication phase.