You misread that. The comma is important. “nor shall be compelled in any criminal case to be a witness against himself,” is the relevant part to encryption. “nor be deprived of life, liberty, or property, without due process of law,” is separate from that. The second clause has to do with warrants, but the first clause is not qualified by the second. IE not even a warrant can compel you to be witness against yourself. Nothing (legally) can compel you to do so.
The source of argument with regard to encryption keys is whether revealing the key is being a witness against yourself or if it’s the same as turning over the key to a physical lock. US courts were conflicted on that, but especially after the recent SCOTUS decision that warrantless searches of cell phones aren’t acceptable, it seems the tide is turning and compelled disclosure of an encryption key is going to be considered compelled testimony. The basis of the cell phone decision was that as use of cell phones and other personal technology has evolved, people have begun to store data on them of a far more personal and private nature than what would be stored in a safe or a lock box. The expectation of privacy that the common person has for those devices is quite high, and thus it’s proper to require LEO to seek a warrant when they feel it necessary to invade that privacy. Similarly, revealing an encryption key is seen to be a much more profound invasion of an individual’s privacy than simply handing over the key to a lock or combination to a physical safe. The analogy to a private code written in notebooks is also on point. You could never be compelled to translate your private papers to aid the police, and I see no reason that providing an encryption key to “translate” the encrypted data should be any difference just because there’s a machine involved in the process.
Assuming that continues to be the case, then no warrant can legally compel you to aid in your own prosecution. The warrant can take the phone away from you for searching in the first place, but nothing can force you to aid in conducting the search. If they can break in, they get it. If not, oh well.