Erase all content and settings - is it "foolproof"?

[Commodore]

Does the "Erase all content and settings" option always wipe everything and puts iDevice into "factory default" state? That is, even if such device was at some point in the past jailbroken (or more precisely - if you restored from a backup of an iPad that was once jailbroken, to a new one that is jailed, and use later on the "Erase all content and settings" on this one, could there still be leftovers on the new one)?

I suppose it depends on how that function works, i.e. does it just wipe out files and folders that are supposed to be user's, ignoring all other "non-standard" folders (therefore leaving them intact), or does it also remove everything that's not supposed to be anywhere outside the regular iOS structure (e.g. /usr/mycustomfolder, /var/mobile/anotherone, /mycommonstorage etc.).

(Just to be clear - I know you're supposed to use DFU + restore from iTunes if you want to wipe a jailbroken iPad. I'm just curious whether there have been any cases where a currently non-jailbroken iDevice would not be completely wiped with the Apple's iOS default option to wipe all.)

 

[J. A.]

I hope this will answer at least a part of your question: http://support.apple.com/kb/ht2110

 

[Commodore]

Thanks, but I read that page just prior to posting this thread. Not enough details for an above-average user (and of course they won't mention jailbreak). However, "Erases user settings and information by removing the encryption key that protects the data" means the data is still there (if you have means to break the encryption).

 

[J. A.]

Sorry, I didn't know that you've already seen this page. I can't help you at all then. You'll have to wait for the experts' opinion.

 

[willerz2]

Not unless it's a custom IPSW used, and not in the sense of a stitched blob/APTicket IPSW, but as an IPSW that has had it's code modified in some way, which is only applicable on pre-A5 devices, or if you have an unexposed exploit/vulnerability to do so. As long as your device is stock, the Erase All Contents and Settings feature will wipe the device, though most likely not as fast as a restore relative in comparison to a moderately or full storage iPhone, and a computer with the latest IPSW for the device downloaded. Jailbroken-restores do not affect the feature as only certain modified plists are carried over, and the Erase All Content and Settings wipe is dependent on the core iOS itself, particularly the boot chain and kernel.

 

[Commodore]

So the new owners, in case they jailbreak the device at some point, shouldn't come across some old Cydia tweaks and/or their settings files, and eventual custom folders and their contents, from the original owner?

By the way, when you use OTA iOS update, does the iDevice keep the .ipsw files on the device (taking up precious space), like iTunes keep them on the computer?