中文摘要：

美国政府在1993年公布的联邦加密标准议案中正式提出了密钥托管的概念。文章首先以公正Diffie—Hellman方案为例，介绍了软件实现密钥托管的方法。在公正Diffie—Hellman方案中，托管机构无法确认其所持有的用户密钥片段的保密性。文章利用理性密码协议分析方法，对其进行了改进，增强了托管方案的合理性和公平性。

英文摘要：

In 1993, The U.S. government put forward the concept of key escrowing in the escrowed encryption standard. This paper, taking fair Diffie-Hellman scheme as an example, provides how to achieve the key escrowing by software. In the fair Diffie-Hellman scheme, escrowing department could not confirm the confidentiality of the users＇ key segments they hold. In this paper, the analytical method of rational cryptographic protocols is used to increase the reasonableness and fairness of the escrowing scheme.