Request info on how SVN client knows about changes on file system

I have a need to distribute files to a local file system on a user's PC, and to monitor them for changes bacically to ensure that we are using the correct version of a particular file at a particular time, and that someone has not changed the file since it was placed on the file system by our application.  Design constraints preclude using a version control system directly, as we need to download large numbers of files in a zip and we need to allow the contents of one zip file to clobber the contents of another zip.  We do however need to validate that any one zip is accurately

It has occurred to me that this problem has already been solved by version control clients like the CVS or Subversion client, which write data to the file system, and use this data to determine if files on the file system have changed and need to be checked in.

Can anyone provide insight on the details on the way in which the SVN client creates the .SVN folder on the file system, what's in it, and how it is used to determine that the file has changed, so that we can learn from it?

Thanks,
Steve