Save encryption as XML

I have a strange problem, I have encrypted my cc # using Rails - works
great, now I need to use that private key to decrypt the # using Visual
Basic - not working so great. Apparently VB has little or no
functionality to decrypt something by giving it a private key, unless
you do it a very weird way, which I am having trouble with. Is there a
way to get at the modulus and the xponent of the key so I can write it
as an xml file so VB will be happy? Thanks,

-S