中文摘要：

在 2005，刘等。建议了改进到 Chien 等。的遥远的用户认证计划用智能卡，攻击阻止平行会议。然而，这篇文章将表明那刘等。的计划对伪装的服务者攻击脆弱并且向前有系统的秘密钥匙秘密问题。因此，由使用柜台而不是时间标记，有更好的安全力量的一个改进计划被建议。建议计划做不仅完成他们的计划是优点，而且由承受就提及的软弱提高它的安全。

英文摘要：

In 2005, Liu et al. proposed an improvement to Chien et al.＇s remote user authentication scheme, using smart cards, to prevent parallel session attack. This article, however, will demonstrate that Liu et al.＇s scheme is vulnerable to masquerading server attack and has the system＇s secret key forward secrecy problem. Therefore, an improved scheme with better security strength, by using counters instead of timestamps, is proposed. The proposed scheme does not only achieve their scheme＇s advantages, but also enhances its security by withstanding the weaknesses just mentioned.