On top of that: How you you distinguish an encrypted document from a data serialized according to a proprietary format? As long as the algorithm to write the d

On top of that: How you you distinguish an encrypted document from a data serialized according to a proprietary format? As long as the algorithm to write the data is unknown and secret, this is essentially a cryptographic algorithm - you can't read the information on disk without the secret, unless you invest a lot of time. Weak crypto, mind you, because we'll probably be able to decrypt it in polynomial time. So suddenly, all storage formats need to be openly documented?