Diffie-Hellman Key Generation

Does anyone know of software available outside the US for generating large (1024-bit or more) Diffie-Hellman keys ? The default key for CTCP is only 512 bits, and I'd like to be able to give out some larger keys (e.g. 1024 and 2048 bits) so that people have a choice of the level of security that they want to use. Alternatively, does anyone have any pre-generated large keys that I can put in there ? Finally, I'm basing this on comments in 'Applied Cryptography' that D-H keys should be at least 512 bits and preferably 1024. How does the difficulty of breaking a D-H exchange with a 512 bit key compare to breaking a 512 bit RSA key ? Mark