Computer Networks

Prac Exercises #17

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 C++ people.

2. Investigate the Unix crypt utility.

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 (I'm not sure about Macs). Investigate what ssh can do for you.

4. Even if you're not tackling Q.4 of assignment 3, you should be aware of the pgp utility available on the department Unix systems. Run pgp and see what it tells you in its usage message. Note that PGP is also widely (and freely) available for PCs and Macs.

5. Investigate skey, available on our departmental Unix systems. What problem does it attempt to solve?

6. Follow some of these cryptography links and learn about the history, the politics and the evolution of cryptography.