Ubercart Credit Card question

If there are any Ubercart users out there that have set it up with a gateway to take credit card payments on their site I have a question.  I notice most of the sites use Paypal but we have a different gateway (Authorize.net) that Drupal supports and would like to use it to receive secure CC payments for merchandise.  Since our chorus is hosting the BHS International contest this year I have been tasked to set up a shopping cart E-commerce system to be able to sell Portland merchandise such as T-Shirts, Pins and other items.
I'm getting the message "Credit card encryption must be configured to accept credit card payments."  So I go to Store Administration > Configuration > Payment Settings >  Edit > Payment Methods.  Under "Credit Card Settings" there is a field to put the path of your encryption key file (which Ubercart will autocreate for you).  I have tried many many paths but it won't accept any of them. 
I have used this format:  
http://senateaires.groupanizer.com/sites/senateaires.groupanizer.com/files/foldername
I think this is the proper path but after reading the documentation on Ubercart's page (http://www.ubercart.org/docs/user/14512/credit_card_settings#security) which states "you should specify a folder that is outside of your document root (i.e. not in your www or public_html directory) where the module can create a key file to encrypt credit card data", I think Ubercart classifies this path as the public area.  But I cannot get access to any other folders above this path so I can create one and use that path for the key file.
I have a feeling I might be blazing a new trail with this credit cart processing business (and not using Paypal).  But if anyone out there has gone through this pain and have figured it out I need your help!  It will be WAY worth it to use our own gateway and not pay Paypal a portion of all of our profits.
Here's the public shopping catalog I have set up for the Portland Convention.  Right now it only accepts payment by check but it's a start.
http://senateaires.groupanizer.com/category/catalog/portland-2012-convention
Thanks,