The problem here is that you have to convince people you're telling the truth. If there are any number of stenographic techniques at your disposal, and only way

The problem here is that you have to convince people you're telling the truth. If there are any number of stenographic techniques at your disposal, and only way to confirm whether you're being honest is if the drive decrypts, then unless that occurs it can't be easily determined whether you were giving a good faith answer or not.