Allowing access to private document to an IP address

Hello,
Is there a way to allow access to an IP address to private document (without logging in)?
For example, I want Copyscape.com to be able to scan my pages for content that may have been posted elsewhere on the web (http://copyscape.com/faqs.php#password)
Thanks in advance for any idea you can share.

The only thing I can think of offhand is to put a snippet call in your template and, in the snippet, check the IP and log the user in in the code.