GNU Privacy Guard
The GNU Privacy Guard (GPG) is a free replacement for the PGP suite of cryptographic software. It is released under the GNU General Public License and was initially developed by Werner Koch. The project is supported by the German government. GPG is completely compliant with the IETF standard for OpenPGP. Current versions of PGP (and Veridis' Filecrypt) are interoperable with OpenPGP compliant systems (eg, GPG) and some older versions are as well. As is common in such situations, not all features of newer software were supported by older software. It is necessary for users to understand those incompatibilities and work around them.
GPG is stable, production-quality software. It is frequently included in free operating systems, such as FreeBSD, OpenBSD, and NetBSD and with nearly all distributions of GNU/Linux as well.
Although the basic GPG program has a command line interface, there exist various front-ends that provide it with a graphical user interface; for example, it has been integrated into KMail and Evolution, the graphical email clients found in the most popular Linux desktops GNOME and KDE. A program known as enigmail allows GPG to be integrated with Mozilla. Note that, because the plug in mechanism is not part of GPG itself and not specified by the Open PGP standard, and because neither the GPG nor Open PGP developers were involved in their development, it is possible that when used as a plug in GPG could become less (or even wholly) insecure. See also similar comments in the article on PGP.
GPG encrypts messages, using asymmetric keypairs individually generated by GPG users. The resulting public keys can be exchanged with other users in a variety of ways, for example via Internet keyservers. They must always be exchanged carefully to prevent identity spoofing by corrupting public key <--> 'owner' identity correspondences. It is also possible to add a cryptographic digital signature to a message, so the message integrity and sender can be verified, if a particular correspondence relied upon has not been corrupted. See the PGP article for a more complete, though still brief, account.
Since GPG is freely distributable, it cannot use patented or otherwise restricted software or algorithms. These include the IDEA encryption algorithm which has been present in PGP almost from the beginning. Instead, it uses a variety of other, non-patented algorithms such as Triple DES. It is still possible to use IDEA in GPG by downloading a (free) plugin for it. Note, however, the earlier comment about the potential effects of add ons to crypto system software.
GPG can also be compiled for other platforms like Mac OS X and Windows due to its open source nature. For Mac OS X, there is a free port called MacGPG which has been adapted to use the OS X user interface and its native class definitions. Cross compilation is not a trivial exercise, but high quality compilers should routinely produce executables which will interoperate correctly with other GPG implementations.
GPG is a hybrid encryption software program in that it uses a combination of conventional symmetric-key cryptography for speed, and public-key cryptography for ease of secure key exchange, typically by using the recipient's public key to encrypt a session key which is only used once. This mode of operation is part of the Open PGP standard and has been part of PGP from its first version.
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Application program | Blogging | ComputerSoftware | Computer software | ElGamal | ElGamal discrete log cryptosystem | El Gamal | El Gamal discrete log cryptosystem | Elgamal discrete logarithm cryptosystem | Enigmail | FriendBlog | FriendBlogs | Len Sassaman | PrettyGoodPrivacy | Pretty Good Privacy | Public-key cryptography | Public key | Public key cryptography | Software | Web log | Weblog | Weblogs | Werner Koch
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