Sn0wbreeze jailbreak and iFaith developer iH8sn0w has finally cracked the hard nut. The hacker has discovered a loophole in Apple’s APTicket system that will assist you to downgrade from iOS 5.1 to iOS 5.0.1 on iPad 2 and iPhone 4S. He is pretty much confident that the method he has devised will also work on A5X processor based iPad 3. But since Apple has yet to release updated iOS for the new iPad, he hasn’t ‘actually’ tested it on the iPad 3. Finally, it will now be possible to restore to any firmware you want on A5 devices, as long as you have the SHSH blobs saved.
Till now saving SHSH blobs with TinyUmbrella wasn’t working for both iPad 2 and iPhone 4S since iOS 5 has new SHSH mechanism (with APTicket). iOS firmware downgrade was only possible from iOS 5.x to iOS 4.x (however, you must have saved SHSH blobs for iOS 4.x) using TinyUmbrella but the tool doesn’t work for downgrading between versions of iOS 5.x (for instance, iOS 5.1 to iOS 5.0.1).
For iPhone 4, iPhone 3GS, iPad G, iPod touch 4G, you can use either iFaith or redsn0w for downgrade between iOS 5.x firmware. Redsn0w is probably the most convenient method for downgrading the non-A5 devices. It actually stitches 5.x blobs to a custom firmware file and use that file to restore to iOS device. We have already posted a guide in detail on how to save APTickets and SHSH Blobs using Redsn0w. You can use it and let us know if you have any issues.
Those who haven’t saved the SHSH blobs for iOS 5.0.1 or iOS 5.0 will not be able to downgrade their A5 based iPhone 4S and iPad 2. Yes, SHSH blobs will ‘always’ be required unless someone finds an untethered bootrom exploit.
Steven hasn’t shared as to when he will be patching or updating his iFaith tool which can then be used to restore iPad 2 or iPhone 4S to 5.0.1 from 5.1 IPSW. We assume that once the jailbreak for iOS 5.1 on A5 based device is achieved, updated iFaith tool will be released to the public.