Config file content management for .net applications

Question

I am looking for a proven approach for management of configuration file (app.config and web.config) and its contents for .NET applications. The objectives are:

1. Keep the file's content encrypted to eliminate unwanted change by unauthorised way.
2. Have a user interface to change tags, values for particular sections
3. Manage which sections are editable

Please let me know approaches taken by you or any standard tool/utility or pattern for the same.