1 引言 Internet从诞生之日起就是一个开放的系统,把许许多多的计算机系统互联起来形成一个庞大的通信网络,但是这种开放性使得Internet中的信息很容易被拦截、监视和窜改,导致人们不愿意使用Internet交流一些敏感或机密信息,如商业信息等。这在一定程度上阻碍了Internet的发展进程。 Internet用户所面临的问题可以归为两大类:信息保密和身份验证。信息保密要求传送的信息在途中不得被修改,而身份验证要求通信的双方确认对方的身份。解决的方法之一是加密,确保信息的保密和安全;二是认证(certification),保证通信是在预期的两者之间进行。公钥加密机制非常适合于In- 1 Introduction Internet has been an open system since the day of its birth, interconnecting a large number of computer systems to form a huge communication network. However, this openness makes information in the Internet easily intercepted, monitored and tampered with, resulting in People do not want to use the Internet to communicate sensitive or confidential information, such as business information. To a certain extent, this hinders the development of the Internet. Internet users face the problems can be grouped into two categories: information security and authentication. The confidentiality of information required to transmit the information shall not be modified on the way, and authentication requires both sides of the communication to confirm each other’s identity. One of the solutions is to encrypt to ensure the confidentiality and security of the information; and second, to ensure that communication is between the two expected. Public key cryptography is well suited to In-