S. Garfinkel, O'Reilly & Associates, PGP: Pretty Good Privacy, O'Reilly & Associates, Inc., 1995.
Michael Johnson, “Lurking with PGP”, Linux Journal, December 1996, Issue 32.
MIT Distribution Site for PGP: http://web.mit.edu/network/pgp.html
The International PGP Home Page: http://www.ifi.uio.no/pgp/
B. Schneier, Applied Cryptography, John Wiley and Sons, Inc., 1994.
COAST Homepage: http://www.cs.purdue.edu/coast/
CERT Coordinating Center: http://www.cert.org/