Secrecy, privacy, security, intrusion

[phb]

@postulative

For number plates, you may want to use a frame that filters certain light spectra. (No, I have no idea how reliable this is.)

And how legal. In Queensland there was a crackdown on filtering/reflecting number plate covers few years ago with fines issued. Obscuring a number plate in any way is an offense in Qld (and assume it is the same in other states).