Barry Steyn over at I’m Still Learning has a nice post on RSA and how it works. Steyn explains the needed mathematical background in small pieces that should be accessible to everyone. At each step he works through a small example so that the reader can follow the process.
If you’ve ever wondered what’s behind RSA, how it works, and what its weaknesses are, this post is an excellent introduction. Steyn even explains modular arithmetic so if the statement 11 divided by 4 equals 2 remainder 3 makes sense to you, you will have no problem following his exposition.