Internet的规模迅速发展，电子邮件是世界上使用最广泛的Internet工具，据统计，在Internet中1／3以上的通信量用于电子邮件系统。正因为如此，电子邮件系统业务的安全──保密和可靠，得到了广泛地重视，为达到电子邮件系统安全要求，最广泛采用的数据包是PGP。本文阐述了PGP原理及其所提供的服务，其中包括密钥，数字签名，压缩，消息加密，ASCⅡarmor，操作次序和公开密钥管理等基本内容。 The rapid development of the Internet scale, e-mail is the world’s most widely used Internet tools, according to statistics, in the Internet more than 1/3 of the traffic for the e-mail system. Because of this, the security of the email system business - secrecy and reliability - has gained wide acceptance and the most widely used data packet is PGP for the security requirements of email systems. This article describes the principles of PGP and the services it provides, including key content, digital signatures, compression, message encryption, ASCⅡarmor, operation order, and public key management.