iMovie or FCP X - possible to make plate number not readable in video?

I'm into automotive photography and since some time videography as well.



I started recording certain videos of super sport cars where the owners are driving on empty roads outside the cities with speeds over the limit as well as drag races and burnouts. (we are making sure that noone is around and that roads are kept empty).



To not get the owners in trouble by burning rubber and driving fast I want to make their plate numbers not readable.



Can iMovie do that (automatically) once the plate number is selected and tracks that throughout the video or do I need FCP X? I hope one of the two can do that without hours of manual work and individual frame adjustment as this would take forever.



I don't k know how you call this function, but I hope that you understand what I am looking for.



Thanks a lot.</div>