You can learn about encryption at Netsurfer Focus on Cryptography and Privacy at www.netsurf.com/nsf/v01/03/nsf.01.03.html. This Web site presents an introduction to cryptography, information about key certification, a discussion of e-mail issues, e-commerce issues, and other resources. One of the most popular and well-publicized encryption methods is Pretty Good Privacy (PGP). You can learn all about PGP at "Getting Started with Encryption: An Introduction to PGP" at www.cs.uchicago.edu/~cbarnard/pgptalk/index.html. This Web site is an online PGP tutorial that was presented at the Computer Professionals for Social Responsibility conference in October 1995. The MIT distribution site for PGP at web.mit.edu/network/pgp.html includes information on how to integrate PGP with mail programs, a link to frequently asked questions, and links to Internet information on PGP, in addition to a link through which you can download a copy of the program.

Interesting books on encryption include Building in Big Brother: The Cryptographic Policy Debate by Lance J. Hoffman (Springer Verlag, 1995), The Computer Privacy Handbook: A Practical Guide to E-Mail Encryption, Data Protection, and PGP Privacy Software by Andre Bacard (Peachpit Press, 1995), and Internet Cryptography by Richard E. Smith (Addison-Wesley, 1997).

The Spartans of ancient Greece might have been the first to use military cryptography, perhaps as early as the fifth century B.C. Since then, cryptography has been used to keep secrets, provide mental exercise, and amuse those who appreciate mathematics and analysis, as well as to preserve and protect military secrets. Are there coded messages in the works of Francis Bacon and Shakespeare? Find out by reading "Cryptology in the 16th and 17th Centuries" at home.att.net/~tleary/cryptolo.htm. Did the poet Edgar Allan Poe really dabble with cryptography? You can learn the answer at the The Edgar Allan Poe Cryptographic Challenge Web site (http://www.bokler.com/eapoe.html). If you're interested in trying your hand at cryptograms, check out Today's Cryptogram and Contest at www.mindspring.com/~fmnshare/today.html. You might also venture over to the Magic Decoder Game at raphael.math.uic.edu/~jeremy/crypt/cgi-bin/
magic-gateway.cgi.