password protect an xml/rss file

[John Smith]

i need to assign an rss/xml file to each user

this file will be accessed most likely through an rss aggregator (user/pass
credentials for file) and not a browser.

how can I password protect the file so that it can only be accessed by a
single user?

I don't want users to share the link to their rss file with other people.

I'd like to be able to monitor how often the rss/xml file is accessed/viewed
so I can determine if the user has shared his/her password to the rss/xml
file with other people

thanks for any info.