摘要： 分析了文献[1]中的一次性口令的身份认证方案，发现由于原方案是一个单向认证协议，因此不能抵抗中间人攻击，该文在不增加计算复杂度的前提下，对原方案进行了改进，使其成为一个安全的双向认证协议，并将其中的关键信息进行了加密保护，改进后的方案克服了原方案存在的安全漏洞，并保留了原方案的所有安全特性，且具有更高的安全性。

关键词: 一次性口令, 身份认证, 中间人攻击, 密码协议

Abstract: Through analysis of the security of the One-time Password scheme mentioned in article[1], this paper finds that this scheme uses a single authentication protocols which can not resist the men-in middle attack. To solve the problem, it proposes an improved scheme—a mutual authentication protocols. The new scheme can conquer the security problem of the original scheme with the same computational complication and hold all security characteristics of the original scheme. So the developed scheme has higher security than the original scheme.

Key words: One-time password, Identity Authentication, Men-in-middle attack, Cryptographic protocols