It represents protection
That's what I think too, which is why I also think I have a problem with it. It seems redundant because privacy (signified by the lock) is protection. Furthermore, a shield with a keyhole in it doesn't really make sense: it isn't a real object or modeled on anything that would have uti beyond the fact that protection and privacy are related concepts.
I really like the idea of using gold or some kind of yellow for the word coin for the obvious reason, but also because it is a lighter color.