How to protect personal documents in my app for the maximum

I want to protect the user's document downloaded via my app. - If I store the files in Document folder of iOS, iTunes will read them, right? - If I store the files in Library or a subdirectory of it, files will be cleaned when the app is upgraded? - The NSFileManager has a NSFileProtectionKey property. But I'm not 开发者_Python百科sure what exactly it can do to protect the files? Does it can prevent other app from reading the user's files?

Overall, I want the files only can be read in my application, other than iTunes or other jailbreak app.

Thanks alot.

Every app is in a SandBox. It means other apps can't access your app files, even from low-level functions.

So they are quite secure.

You can actually see this with this little app, available from the AppStore:

http://www.eosgarden.com/en/freeware/filesystem/

Apps are located in /var/mobile