Data Protection iOS 4 file encryption

Question

Hi,
I need to ask a question about the "data protection" of iOS 4.0.
I'm developing an application that downloads files from a server. Then downloaded files, using iOS 4 data protection, I'm going to write them as protected (encrypted) using the method "writeToFile: options: error "( the options attribute is NSDataWritingFileProtectionComplete). I mean in a few lines of code can mark a file as readable and therefore not protected when the iPad is in blocking state:
NSDictionary * FileAttributes = [NSDictionary dictionaryWithObject:
NSFileProtectionComplete forKey: NSFileProtectionKey];
NSFileManager * fm = [NSFileManager defaultManager];
[fm SetAttributes: FileAttributes ofItemAtPath: pathFileToWrite error: nil];
NSData * fileData = [fm contentsAtPath: pathFileToRead];
* NSError writeError = nil;
[fileData writeToFile: pathFileToWrite options: NSDataWritingFileProtectionComplete error: & writeError];
In this situation I've secure files and they are stored in the file system.
At this point, when the device goes to block status, iPad protected file should not be accessible, because the files appears to be protected. My application can access the file only when the iPad is an unblock status.
The questions:
1) How do I read the file (from simulator), while the iPad is blocked, so as to realize that actually the file is protected and thus access to the file from my app is impossible? I think to implement a method to read the file only after the device (simulator iPad) is on block status, then implement a timer to start reading the file only when post-lock device.
2) The next phase of my work is to communicate to my application that the device iPad is going to go into a locked state and then all encrypted files are not available for reading and access. Doing so would take steps to avoid having to use the APP file while the device is faulty.
Reading the documentation iOS 4 I saw that there are two methods:
- applicationProtectedDataWillBecomeUnavailable
- applicationProtecedDataDisBecomeAvailable
At this point I should implement these two methods in the code to release resources so as to prevent the file my application to read the file if the device is locked.
How can I implement this code inside the methods?
thanks in advance for your support!!
daniele

Answer 1

I was able to fix the issue. I had to manually put the phone in restore mode by holding the power button and the home button until the power turned off while the phone was still plugged into the computer, then when the phone turned off continue holding the home button until you hear the computer recognize the device. Then navigate to the back up folder that is described earlier and cut out all of the back up folders and paste them on your desktop. Then iTunes said that a device was recognized in restore mode or something like that and you click yes to restore. After this happen the iPhone will go through the processes of restoring the phone. When it finishes it will start like a brand new device and it will be updated to the OS4.0. You will then need to go through the tabs at the top of the iPhone sync window and re check all of the items that you want synced to your phone. The only data that was totally lost was my pictures, but after the iPhone finishes reloading, you may be able to go back to the desktop and cut the backup folders and paste them back into the backup folder and restore your phone from a previous back up and you may still be able to recover those photos. This worked for me so I hope it works for all of you as well. Thanks!