It is not that clear cut. You don't have to unlock the safe, you have to provide the key to unlock the safe. If the key only exists in your mind, and the contents of your mind are protected by the Fifth Amendment, then it is likely that you don't have to provide the key.
You are further protected by the fact that we don't have mind-reading devices yet. (People are often forgetful under stress, so it follows that you could forget your difficult-to-remember password under the stress of arrest and trial.)
Yes, there is US v. Boucher. That is a very special case, however, and District Court rulings are far from definitive.
The "contents of your mind" are not protected by the 5th amendment. The part of the 5th that everyone remembers and obsesses about only prevents the state from compelling you to testify against yourself.
Here is the example which is more appropriate to this discussion: The state contends that Bernie Madoff may have stashed billions in offshore bank accounts, the state has proof that these accounts exist and that he accessed them on a regular basis. The state (specifically a judge) can compel him to produce the account numbers and access codes to enable prosecutors and investigators to examine the account activity. If he refuses the judge has the power to place him in jail (for contempt of court) until such time as he provides the information to the court that it feels is necessary to render a fair judgement.
Sure, but the judge can hold you in contempt for anything. There was one judge who put his entire courtroom in jail because someone's phone rang and nobody admitted to it. He is no longer allowed to be a judge.
Anyway, this is why there exists deniable encryption. The example cases usually involve someone beating you with a rubber hose, but contempt is a much more realistic outcome. So you spend a day or to in jail, "decide to remember" your key, and everyone thinks you have done them a big favor. In reality your cache of bomb-making plans and maps of the white house are still several enctyped volumes deep. It looks like you were coerced into cooperating, but you actually didn't.
The contents of your mind are a bitch -- nobody knows them but you.
But really, in real life, the state would have to prove that you don't actually have an unformated drive containing random data. I have a few disks like this; they once contained useful data, but I since upgraded them, and now they are useless. They were overwritten with random data, but at one point had real data. Do I risk indefinite imprisonment for this? Hopefully not. (The government mandates that government agencies keep their unwanted disks in this state.)
Bullshit. If providing information incriminates yourself you do not have to provide it. If those account numbers are on a piece of paper, sure he has to produce the paper. But not if it's in his brain only.
You are further protected by the fact that we don't have mind-reading devices yet. (People are often forgetful under stress, so it follows that you could forget your difficult-to-remember password under the stress of arrest and trial.)
Yes, there is US v. Boucher. That is a very special case, however, and District Court rulings are far from definitive.