Make sure you know which of the viruses are hoaxes. Check out Symantec's site and the F-Secure Corporation site.
The distributed denial of service (DDOS) attack on Yahoo, Amazon, eBay and others in February of 2000 was the first big attack on multiple e-commerce sites. Read more about it.
To learn more about PKI, check out Netscape's site.
More information about DES, straight from the horse's mouth (the government).
Read about the new bill that allows digital signatures for electronic documents.
Good set of tutorials on spread spectrum technology by Spread Spectrum Scene.