Abbreviated PGP. A popular public-key encryption and digital certificate program, originally written by Phil Zimmermann, available at no charge from certain Internet sites.
PGP uses Diffie-Hellman public-key algorithms, is available for Microsoft Windows and Macintosh platforms, and works with most popular messaging applications such as Microsoft Exchange, Eudora, and Claris Emailer for the Macintosh.
See also Privacy Enhanced Mail; RSA Data Security.