Computer Networks

Prac Exercises #18

1. If you've got a bit of spare time (;-) try writing a small program to implement XOR encryption. You should be able to do a minimal one in just a few lines of C, maybe a few more for you C++ and Java people.

2. Investigate the Unix crypt utility, or the equivalent on your own machine..

3. In the lecture, the risks of using TELNET to log in across an insecure network were mentioned. One solution to this is to use the ssh utility, available on all of the departmental Unix systems, and also available for PCs, Macs and even for PalmPilots. Investigate what ssh can do for you.

4. Everyone should know about pgp. It's a free download for virtually all platforms, and is available on our Unix systems. Run pgp and see how helpful it is.

5. Investigate skey on a nearby Unix system. What problem does it attempt to solve?

6. Follow some of the cryptography links on this page and learn about the history, the politics and the evolution of cryptography.