That article relies on Doe v. United States, 487 U.S. 201 (1988)[1], in which the Supreme Court found that a suspect could be compelled to sign a form authorizing banks to disclose records of any accounts over which he had a right of withdrawal, because 'neither the form nor its execution communicates any factual assertions, implicit or explicit, or conveys any information to the Government.' Applying that decision, a federal circuit court has already decided that the Fifth Amendment rights of the suspect in this case have not been infringed: United States v. Apple Mac Pro Computer, 851 F.3d 238 (2017)[2]. So, while the question is currently the subject of a petition to the Supreme Court, it is not accurate to say that judges agree that revealing a combination, or decrypting an encrypted volume, 'delves into the mind' so that compelling someone to do so would violate the Fifth Amendment.
No, I meant judges in this particular case, not all judges. This is the key part.
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.”
Being compelled to reveal the combination to a wall safe they consider a violation of the 5th amendment. Revealing the combination to a wall safe is much more like revealing a password than surrendering a key.
That's a fair point, and the last sentence of my previous reply should be qualified: compelling someone to reveal the combination to a wall safe is not necessarily a violation of the Fifth Amendment. In this case, the court decided that the 'foregone conclusion' exception in Fisher v. United States, 425 U.S. 391 (1976)[1] applies. In Fisher, the court acknowledged that producing documents in response to a subpoena can be testimonial, because it 'tacitly concedes the existence [and possession] of the papers demanded.' But when the existence of the location of the documents are a foregone conclusion, the testimonial aspect of the production of documents – the tacit concession as to their existence – adds 'little or nothing to the sum total of the Government's information.'
As you suggested, compulsory key disclosure can be a violation of the Fifth Amendment, and here the court referred to an example of that in In re Grand Jury Subpoena Duces Tecum Dated Mar. 25, 2011, 670 F.3d 1335 (2012)[2]. The difference was that in In re Grand Jury Subpoena, there was no evidence that the TrueCrypt volumes contained any data, and no evidence that the suspect could actually decrypt them.
[1] https://www.law.cornell.edu/supremecourt/text/487/201
[2] http://caselaw.findlaw.com/us-3rd-circuit/1853477.html