Contempt of court

I gather that a court can order you to produce the means to decrypt cyphertext that the court has ruled is evidence. This would imply that the giving of the means to decrypt (which could simply be the uttering of a password) is not considered testimony, because you cannot be forced to give testimony under the 5th amendment. Is there a court decision on point for this issue. In another but similar context, can a court order you to give it the combination of a safe, that contains evidence? I suspect, if that is the case, then there is no 5th amendment protection against being so ordered to produce the means to decrypt messages, documents etc.