Rag doll: so long as they can manipulate your uncooperative unresisting body to do something (apply thumbprint, get DNA sample), they can order you to cooperate. They cannot, however, compel you to do something which they otherwise have no case without.
Sawz-all: so long as getting into a safe (or whatever) is just a normal matter of time and money, they can order you to open it. If, however, "opening" an encrypted volume or some such by brute force will take something on the order of heat death of the universe, and otherwise they have no case, you can stay silent.
under some circumstances, they could. the "foregone conclusions" doctrine says that if they know 1) what the contents say, 2) that those contents are incriminating, 3) that you can translate it, and 4) can prove 1-3, then yes, then can compel you to do translate / decrypt.
See Footnote 19: "If in the case at hand, for example, the Government could prove that it had knowledge of the files encrypted on Doe’s hard drives, that Doe possessed the files, and that they were authentic, it could compel Doe to produce the contents of the files even though it had no independent source from which it could obtain the files."