Your thinking to hard, just slap some mud on your plate and say you drive on a dirt road.

Committing an illegal and regularly enforced crime of driving with an obstructed license plate seems like a poor plan to try and defend your right to an abstract sense of privacy.

As I've said time and tim again: Hacks and technological tricks are not the right way to fight civil rights violations. It has to happen through the legal system. If you're just hacking your way around bad laws, you are setting yourself up to get in trouble somewhere down the road.

If that could be done, someone would be doing it to foil speed cameras and red light cameras already.

Well, they are. Google "red light spray" or something similar. I think it may be illegal in some jurisdictions.