This WordPress plugin by alekarsovski and ctlt-dev allows the user to generate feed keys for their private sites. Sites are defined as private as long as their privacy settings are set below the “I would like to block search engines, but allow normal visitors” option. PLEASE NOTE that this plugin has only been tested in conjunction with the “Network Privacy” plugin; while other privacy settings plugins should theoretically work, they have not been tested. Ensuring integration with other privacy plugins is a goal for the next update.
To ACTIVATE a feed key for your private site/blog feed:
Activate the “Feed Key Generator” plugin
Go to the “Privacy Settings” page; Dashboard -> Settings -> Privacy
Ensure your site/blog’s privacy settings are set below the “I would like to block search engines, but allow normal visitors” option
Select the “Activate Feed Key” option from the dropdown
Click on the “Save Changes” button
All of the site feeds should now be protected by your new feed key. The complete feed URL can be found on the “Privacy Settings” dashboard page (if it appears grayed out it means that the feed key is not active).
More info and download: http://wordpress.org/extend/plugins/feed-key-generator/