RSA encryption/decryption in prolog

I need to know how to write that program i wrote as the subject >.< so if someone can plz help that would be grreeeaaattttt.

1) Produce two very large prime numbers
2) multiply them, let product be n
3) ???
4) Send key to A, A can then use it to encrypt stuff
4) A sends stuff to B, B can use secret key to decrypt A's cipher.