I don't reside in the USA and I don't know the US law. After reading a certain amount of comments seems that the heart of the discussion is the fifth emendament

I don't reside in the USA and I don't know the US law. After reading a certain amount of comments seems that the heart of the discussion is the fifth emendament. I agree that if the 5th emendament protects you from giving the combination of a safe logically follows that the same applies for encription passwords. But I don't agree with the root of this argumentation: if a court has a valid reason to think that a safe contains evidence that is relevant for the lawsuit, why should make any difference if the safe is locked with a physical key or with a combination? Somebody who has a different opinion could please explain me his point?