Extract CC info for XML data feed

We have a client that would like us to develop an XML feed which they can use with their accounting software to fulfill orders. I have programmed everything to spec, except with the credit card info. How can I decrypt the credit card info that I'm looking at in the cscart_order_data table? I'm building this script in the /private/ directory of the server so there is no security concerns. I just need to know how to do something with that long, crypted string I'm seeing in that table and extract the necessary payment information.