http://www.gnupg.org/ GnuPG is a complete and free replacement for PGP. Because it does not use the patented IDEA algorithm, it can be used without any restrictions. GnuPG is a RFC2440 (OpenPGP) compliant application. PGP, on which OpenPGP is based, was originally developed by Philip Zimmermann; see his page for background information on PGP.