What is OpenPGP and GnuPG (GPG)?
OpenPGP is on the Internet Standards Track and is under active development. The current specification is RFC 4880 (November 2007), the successor to RFC 2440. Many e-mail clients provide OpenPGP-compliant email security as described in RFC 3156.
The Free Software Foundation has developed its own OpenPGP-compliant program called GNU Privacy Guard (abbreviated GnuPG or GPG). GnuPG is freely available together with all source code under the GNU General Public License (GPL) and is maintained separately from several Graphical User Interfaces (GUIs) that interact with the GnuPG library for encryption, decryption and signing functions.