[btouellette]

Courts have ruled that providing a password to decrypt something is not in itself testimony and isn't protected by the 5th amendment.

Judges can certainly hold you in court indefinitely on a contempt of court charge as well. Considering the nature of the charges that this typically comes up in (see Francis Rawls) I wouldn't count on trying to make it a civil rights issue doing much in your favor.

[jki275]

Other courts have ruled the other way on that. It is not settled law.

[russdpale]

But what if someone really does forget the key? They are just jailed forever?