
This is the Title of the Book, eMatter Edition
Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.
A Brief Introduction to Email Encryption
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PGP, short for “Pretty Good Privacy,” is the older and more popular of the two tech-
nologies. The other, S/MIME, is rapidly gaining ground, thanks at least in part to the
fact that support for it is built into Microsoft Exchange and Outlook.
PGP and GnuPG
The brainchild of hacker saint Phil Zimmerman, PGP was the first email encryption
tool to gain anything resembling widespread popularity, and to this day, it is used all
over the world. PGP exists in both free and commercial versions, but over its long
history it has been, at various times, illegal for export from the U.S.; free for noncom-
mercial use only; closed source; and in limbo (neither being sold as a commercial
product or available for use in a free version).
Happily, PGP is now back to being actively maintained both as a commercial prod-
uct and in a free-for-noncommercial-use version (see http://www.pgp.com/products/
freeware.html for more information about PGP Freeware). However, for all of the
reasons I just listed, even the ones that no longer apply, many people have switched
from PGP to a 100% free and open source alternative: the GNU Privacy Guard, a.k.a.
GnuPG (http://gnupg.org).
GnuPG is completely compliant with the OpenPGP protocol that PGP uses, but
unlike PGP, GnuPG ...