tar / pack `a-r` "unreadable" files

If there are files unreadable even to the owner (chmod a-r), tar and other tools will throw errors when creating an archive. However, these files could be updated with chmod u+r before archiving, and chmod u-r after unpacking — so they are not actually unreadable.

How can such files be archived with their exact permissions? I guess one generate a permissions-restore script (with stat), run chmod u+r, run tar, and keep both the archive and the permissions script. Actually, mtime would have to be saved as well (since chmod destroys it). Anything simpler?