The compelling of revealing a safe's combination is protected in prior cases (I liked on earlier in this thread but I'll quote it again)
We do not disagree with the dissent that “[t]he expression of the contents of an individual’s mind” is testimonial communication for purposes of the Fifth Amendment. … We simply disagree with the dissent’s conclusion that the execution of the consent directive at issue here forced petitioner to express the contents of his mind. In our view, such compulsion is more like “be[ing] forced to surrender a key to a strongbox containing incriminating documents” than it is like “be[ing] compelled to reveal the combination to [petitioner’s] wall safe.”
Of course, the Supreme Court hasn't ruled on it as far as I know, but it's an interesting case. I'd like the SCOTUS to rule on it.
We do not disagree with the dissent that “[t]he expression of the contents of an individual’s mind” is testimonial communication for purposes of the Fifth Amendment. … We simply disagree with the dissent’s conclusion that the execution of the consent directive at issue here forced petitioner to express the contents of his mind. In our view, such compulsion is more like “be[ing] forced to surrender a key to a strongbox containing incriminating documents” than it is like “be[ing] compelled to reveal the combination to [petitioner’s] wall safe.”
Of course, the Supreme Court hasn't ruled on it as far as I know, but it's an interesting case. I'd like the SCOTUS to rule on it.