Since we're studying discrete mathematics in school, and currently reading about modular mathematics and RSA encryption, I thought it would be a nice exercise to whip something up in Java. I didn't want to take advantage of the various built in keypair generators in the JDK, but used a couple of handy methods in the BigInteger class instead.
Nothing fancy. Works only with integers, for the time being.
More about RSA: http://en.wikipedia.org/wiki/RSA_(algorithm)