Where can I find useful data for cryptography/coding theory?
Generating prime integers and computing things modulo integers is easy with a programming language which features support for big integers. I usually use Java: it includes java.math.BigInteger, with which one can:


generate prime integers of any length;
do all basic operations, including modular reduction (mod() method);
compute modular inverses (modInverse());
compute modular exponentiations (modPow()).


For irreducible polynomials, things are more complex: Java does not offer a generic method for testing irreducibility of polynomials (or, for that matter, anything related to polynomials). I do have my own library but it is not generally available (I implemented it for a customer). However, my friend Google points out that this library appears to be fairly complete in that area.