GPG, or GnuPG, is GNU Privacy Guard. GnuPG is a complete and free replacement for PGP.

Gpg4win is an installer package for GPG that adds a graphical shell and plugins for Microsoft Outlook and Windows Explorer.

Because GPG does not use the patented IDEA algorithm, it can be used without any restrictions.

GnuPG is a RFC2440 (OpenPGP Message Format) compliant application.

GPG Encryption Protocol Support

GnuPG supports the ElGamal, DSA, RSA, AES, 3DES, Blowfish, Twofish, CAST5, MD5, SHA-1, RIPE-MD-160 and TIGER algorithms.

Additional Reading on GPG

For more information on GnuPG, refer to the GPG FAQ.