Yes if you use a lock with a key you can be forced by the court to produce it (if they can satisfy a judge that its in your possession), however, if you use a c

Yes if you use a lock with a key you can be forced by the court to produce it (if they can satisfy a judge that its in your possession), however, if you use a combination lock you cannot be compelled to testify as to the combination. (IANAL, that's just what I've read)