Secure Sockets Layer Protocol
http://www.netscape.com/newsref/std/sslref.html

I Broke Hal's SSL Challenge
http://pauillac.inria.fr/~doligez/ssl/

NCSA: Using PEM/PGP
http://hoohoo.ncsa.uiuc.edu/docs/PEMPGP.html

Secure HTTP
http://www.eit.com/creations/s-http/

Security Tools
http://ciac.llnl.gov/ciac/ToolsUnixNetSec.html