摘要： 密钥交换是通信双方建立会话密钥的过程，Diffie-Hellman 协议是一种有代表性的算法，但是这种算法不能够抵抗中间人攻击。为了抵抗中间人攻击，陆续出现了几种具有身份认证功能的算法，但是这些算法运算比较复杂。Seo 等提出了一种简单的算法（SAKA），可以抵抗中间人攻击，并且运算简单。但是SAKA 以及其的增强算法均有缺陷，该文提出了一种改进算法，在具有原有协议优点的同时可以避免这些缺陷。

关键词: 密钥协商；认证；中间人攻击

Abstract: Key agreement is the procedure that the two sides of the communication negotiate a session key. Diffie-Hellman key agreement protocol is well known, but this protocol can not resist man-in-the-middle(MID) attack. Several protocols that can escape MID attack have been proposed. Those protocols are complicated. A simple authenticated key agreement algorithm (SAKA) and its enhanced protocols are developed. They are very simple, but some weaknesses are founded. A new protocol based on SAKA is proposed in this paper, which can make up these weaknesses.

Key words: Key agreement; Authentication; Man-in-the-middle attack