You do have me confused with Mike Godwin. I did write:

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If the key itself had embedded testimony that was incriminating, then it is possible one could invoke the 5th amendment to avoid disclosure of the key. But, I suppose a court could do an end run around that by giving limited use immunity for the incriminating content of the key. Comments?

But the rest of your questions refer to Mike Godwin. My guess is that one could be compelled to reveal the combination to a lock because the combination is not testimony. I'm sure that govenment lawyers would argue that a key is not testimony, just as a combination to a safe is not testimony. Perhaps some research would turn up the answer to this question. There is also the matter of discovery in civil actions. If one had financial records in encrypted form, a court could order you disclose the key under the threat of civil contempt. Civil contempt can be worse than criminal contempt. The court can ruin you financially and keep you in jail until you comply with the order. Mike.