My understanding (also not a lawyer) is that passwords are protected under the 5th amendment when the very act of giving them is testimonial. Two cases where this appears true:
1) Your password is "ITotallyKilledThoseTwentyPeople", e.g. the password contains testimonial evidence. This can probably be circumvented by allowing the defendant to enter their password privately.
2) Your lawyer successfully argues that the very admission of knowing the password to a thing is testimonial. In other words, let's say the feds find an encrypted hard drive labelled "child pornography" under the couch at your apartment. If your argument is that a friend left it there, and the feds can't prove otherwise, then the very act of decrypting that drive would be an admission that it's yours, and hence a violation of the fifth.
It'll be interesting to see where law settles in this area. One thing that seems certain: if the gov't can prove you know a password, they can force you to use it (assuming use is possible without disclosure).
Your understanding jives with my understanding. But in this case the government would likely argue that giving up the password which prove Ulbricht controls the BTC wallets would not be testimonial, as the government already knows he's responsible from the other evidence they have (both already mentioned in the indictment, and yet to be revealed publically).
I think your second example makes sense, but I have seen a lot of discussion of the first and the conclusion is mostly that your passwords is not protected then. Basically, you could either enter the password, or you could even give it to the court and the password itself would not be able to be used as evidence.
1) Your password is "ITotallyKilledThoseTwentyPeople", e.g. the password contains testimonial evidence. This can probably be circumvented by allowing the defendant to enter their password privately.
2) Your lawyer successfully argues that the very admission of knowing the password to a thing is testimonial. In other words, let's say the feds find an encrypted hard drive labelled "child pornography" under the couch at your apartment. If your argument is that a friend left it there, and the feds can't prove otherwise, then the very act of decrypting that drive would be an admission that it's yours, and hence a violation of the fifth.
It'll be interesting to see where law settles in this area. One thing that seems certain: if the gov't can prove you know a password, they can force you to use it (assuming use is possible without disclosure).