How far can court orders go? Let's say he was a crooked accountant and the police couldn't understand his spreadsheet. Is he obligated to show him what he was

How far can court orders go? Let's say he was a crooked accountant and the police couldn't understand his spreadsheet. Is he obligated to show him what he was doing? To me this is what the disk encryption is like. The cops can't understand how to read the disk. Is he obligated to help them? What if the pictures in there are encoded using a weird format? Should he be forced to produce a program to read them?