Well, you obviously can't prove that there is no more data. However if you have a standard encrypted file, the government knows that there's something you're no

Well, you obviously can't prove that there is no more data. However if you have a standard encrypted file, the government knows that there's something you're not telling them. However if you've already given them one key, they can't be sure that there's any more keys for you to give. So they don't know whether to give up. You can get more secure and have 3 levels, 1: backup of important, sensitive documents (like a scan of your passport & banking details, which you obviously just don't want to leave lying around), 2: Homemade fetish porn 3: Subversive materials.