> Public-key cryptography is magic. Public key cryptography is kind of magic, but the basic piece that makes everything work isn't too hard. It's been a while

> Public-key cryptography is magic. Public key cryptography is kind of magic, but the basic piece that makes everything work isn't too hard. It's been a while since I took discrete math, so this is a bit rusty, but it should get you in the right direction. It's modular multiplication in a field. If you take a small field and make a times table, you can see the magic. All of the factors that are relatively prime to the modulus will have a pattern that you F times X is only equal to F times Y if X and Y are equal. There will also be a multiplicative inverse so that F times X time I equals X for all X; because of commutation I times X times F also equals X. When you've determined an F and an I, you give your correspondent F and keep I --- then if you multiply your message by F, they multiply it by I and get back the message. If they want to send you a message, they multiply it by I and send it, then you multiply it by F. There's some other stuff, but that's the magic part, IMHO. You just have to use a bigger field and some other stuff I forgot. ;)