GPG4Win is a free collection of tools for performing pgp-compatible encryption of text files and email. It installs both commandline gnupg tools and a graphical front end utility for managing keys and and a very nice tray based tool for doing general stuff. It's sort of a minimalist version of pgp if you don't need the full desktop tool (commercial pgp tools: here).
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GnuPG is the GNU project's complete and free implementation of the OpenPGP standard as defined by RFC4880 . GnuPG allows to encrypt and sign your data and communication, features a versatile key managment system as well as access modules for all kind of public key directories. GnuPG, also known as GPG, is a command line tool with features for easy integration with other applications. A wealth of frontend applications and libraries are available. Version 2 of GnuPG also provides support for S/MIME.
GnuPG is Free Software (meaning that it respects your freedom). It can be freely used, modified and distributed under the terms of the GNU General Public License .
GnuPG comes in two flavours: 1.4.8 is the well known and portable standalone version, whereas 2.0.8 is the enhanced and somewhat harder to build version.
Project Gpg4win provides a Windows version of GnuPG. It is nicely integrated into a installer and features several frontends as well as (German) manuals.
