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## 2 Prerequisites

PGG requires at least one implementation of privacy guard system. This document assumes that you have already obtained and installed them and that you are familiar with its basic functions.

By default, PGG uses GnuPG. If you are new to such a system, I recommend that you should look over the GNU Privacy Handbook (GPH) which is available at http://www.gnupg.org/documentation/.

When using GnuPG, we recommend the use of the `gpg-agent` program, which is distributed with versions 2.0 and later of GnuPG. This is a daemon to manage private keys independently from any protocol, and provides the most secure way to input and cache your passphrases (see Caching passphrase). By default, PGG will attempt to use `gpg-agent` if it is running. See Invoking GPG-AGENT in Using the GNU Privacy Guard.

PGG also supports Pretty Good Privacy version 2 or version 5.