GnuPG是「OpenPGP标准」（由RFC4880定义）的完整实现。
GnuPG允许数据和通信进行加密及签名，具有多功能的密钥管理系统以及各种公共密钥目录的访问模块。
GnuPG也称为GPG，是一种命令行工具，具有与其他应用程序轻松集成的功能。具有丰富的前端应用程序和库可用。
GnuPG还提供对S/MIME和Secure Shell（ssh）的支持。
GnuPG is GNU’s tool for secure communication and data storage.
It can be used to encrypt data and to create digital signatures.
It includes an advanced key management facility and is compliant
with the proposed OpenPGP Internet standard as described in RFC4880.
安装程序
通过仓库安装
#!/bin/bash ############################################################ # Kali GNU/Linux Rolling ############################################################ apt-get install gpg gunpg
通过源码安装
参考BLFS1.10/GnuPG-2.1.15：http://www.linuxfromscratch.org/blfs/view/7.10/postlfs/gnupg.html
安装的可执行程序
addgnupghome，is used to create and populate user’s ~/.gnupg directories
applygnupgdefaults，is a wrapper script used to run gpgconf with the –apply-defaults parameter on all user’s GnuPG home directories.
dirmngr，is a tool that takes care of accessing the OpenPGP keyservers.
dirmngr-client，is a tool to contact a running dirmngr and test whether a certificate has been revoked.
g13，is a tool to create, mount or unmount an encrypted file system container (optional).
gpg-agent，is a daemon used to manage secret (private) keys independently from any protocol. It is used as a backend for gpg2 and gpgsm as well as for a couple of other utilities.
gpg-connect-agent，is a utility used to communicate with a running gpg-agent.
gpg，指向gpg2的软连接，用于兼容GnuPG的第一个版本。
gpg2，是「GNU隐私卫士」（GnuPG – GNU Privacy Guard）的OpenPGP部分。这是一个使用OpenPGP标准来提供数字加密和签名服务的工具。
gpgconf，is a utility used to automatically and reasonably safely query and modify configuration files in the ~/.gnupg home directory. It is designed not to be invoked manually by the user, but automatically by graphical user interfaces.
gpgparsemail，is a utility currently only useful for debugging. Run it with –help for usage information.
gpgscm，executes the given scheme program or spawns an interactive shell.
gpgsm，is a tool similar to gpg2 used to provide digital encryption and signing services on X.509 certificates and the CMS protocol. It is mainly used as a backend for S/MIME mail processing.
gpgtar，is a tool to encrypt or sign files into an archive.
gpgv，(optional) is a symlink to gpgv2 for compatibility with the first version of GnuPG.
gpgv2，is a verify only version of gpg2.
kbxutil，is used to list, export and import Keybox data.
symcryptrun，is a simple symmetric encryption tool.
watchgnupg，is used to listen to a Unix Domain socket created by any of the GnuPG tools.
参考文献
GPG主页：https://www.gnupg.org/