GnuPG or the GNU Privacy Guard or GPG is GNU's tool for secure communication and data storage. This software is mainly used to encrypt data and to create digital signatures.

GnuPG includes an advanced key management facility and is compliant with the proposed OpenPGP Internet standards as described in RFC2440. It is a complete and free replacement of PGP. Since it does not use any patented algorithms, it can be used without any restrictions.

The first version of GnuPG i.e. version 1.0.0 was released on 7th September 1999. However, the current version is GnuPG 1.4.1.

GnuPG is Free Software. It can be freely used, modified and distributed under the terms of the GNU General Public License.

GnuPG is a command line tool without any graphical stuff. It is used directly from the command prompt, from shell scripts or by other programs. While using from command line, it provides an interactive menu system.

Following are some of the key features of GnuPG:
· Full replacement of PGP.
· Does not use any patented algorithms.
· Can be used as a filter program.
· Full OpenPGP implementation
· Better functionality than PGP and some security enhancements over PGP 2.
· Decrypts and verifies PGP 5, 6 and 7 messages.
· Supports ElGamal, DSA, RSA, AES, 3DES, Blowfish, Twofish, CAST5, MD5, SHA-1, RIPE-MD-160 and TIGER.
· Supports key and signature expiration dates.
· Supports a large number of languages