一、前言六十年代末,七十年代初以来,随着现代计算机的迅速发展和通信手段的多样化,推动了所谓信息革命的蓬勃发展。在这种形式下,人们普遍地使用了计算机来存贮和发送信息;卫星通信和国际电报网的发展,跨国公司、银行等部门的通信系统遍及世界各地;微波接力通信方式已取代地下电缆而被广泛采用。由于这些通信系统容易遭受敌方的窃听和干予,所以出于保密方面的考虑,要求对某些通信和计算机存储和发送的数据加以保护,以便防止高度机密的数据被窃取与滥用。基于这个目的,美国、英国、日本、 I. Introduction Since the late 1960s and early 1970s, with the rapid development of modern computers and the diversification of means of communication, the so-called information revolution has been promoted. In this form, computers are commonly used to store and transmit information; the development of satellite communications and international telegraph networks; the communication systems of multinational corporations, banks and other departments are spread all over the world; the microwave relay communication has replaced the underground cables Is widely used. Because of their vulnerability to eavesdropping and interference by the enemy, these communications systems require confidentiality considerations to protect certain communications and data stored and transmitted by computers in order to prevent theft and abuse of highly confidential data. For this purpose, the United States, Britain, Japan,