File restrictions on blockstack

Is there a way I can implement a restriction of accessing a file within an Application? Say I had application M but I don’t want all of the files a user has in relation to M to be accessible to others who use M. I’m been reading about Blockstack for about two days now and I’m thinking of implementing it’s storage with my iOS app, sorry if this is in the wrong section!

You can encrypt it so only the user (within the app) can access it – that’s the default way putFile works anyways, you actually have to specify if you want it to be unencrypted and therefore “parseable” by the public (as technically all files are viewable, but most are useless, e.x. this graphite document: