This article is from the alt.security.keydist FAQ, by Michael Bauser faqs@bauser.com with numerous contributions by others.
GPG is available at http://www.gnupg.org/
PGP is available at http://www.pgp.com/ and http://www.pgpi.org/
Puffer is available from http://www.briggsoft.com/
RIPEM is available at http://www.cpsr.org/cpsr/privacy/crypto/tools/ripem/
InvisiMail and Sifr are apparently no longer available.
 
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