Well, it sounds very exciting when we here that it is possible to downgrade from iOS 4.0.2 to iOS 4.0.1 or iOS 4.0 without SHSH Blobs. So, in previous tutorials (Mac / Win), I have mentioned that there is a possibility of downgrading your iOS 4.0.2 running devices to iOS 4.0.1 to iOS 4.0. Well, trying that method will not hurt because, anyway you are stuck with iOS 4.0.2 for now. If it works, you can go ahead and Jailbreak it. If not you can get to your previous state (iOS 4.0.2).
Semaphone, the man behind Tiny Umbrella/Firmware Umbrella shared his thought on Downgrading iOS 4.0.2 to iOS 4.0.1 / iOS 4.0 without SHSH Blob. Well, according to him it is not at all possible.. This is what he says..

Let me get this out first.

  1. This is not a miracle, at least not in the sense you all hope for
  2. SHSHs are STILL required for any iPhone 4, iPhone 3GS, iPad, iPod Touch 3G, and iPod Touch 2G (MC Model)
  3. There is NO way around this… unfortunately this method included.

Let me start by explaining something very important. The buildmanifest is used by iTunes to build much of the TSS request that is used to obtain your SHSH for any given firmware revision. Unfortunately, the BuildNumber has no part to play in the request for SHSH. All that you ended up doing in following these directions is request 4.0.1 SHSH blobs. THAT IS ALL. Since every single one of you that got this to work changed your hosts file to point to Cydia, Cydia responded to the TSS request with an SHSH blob that was ALREADY “on-file”. There was no magic. There was no miracle, apart from the lucky break that your device had been put on Cydia’s SHSH request list at some time in the distant past.

That’s it in a nutshell folks. There was no amazing technique for bypassing Apple’s TSS. There was no amazing exploit that exists in DFU mode allowing for 4.0.2 -> 4.0.1 downgrading. It’s simple; Cydia had your SHSH because at sometime in the past either:

  • Someone saved your SHSH with that device using TinyUmbrella and the default options
  • Someone restored that device with Cydia in the hosts pointing to gs.apple.com
  • Someone jailbroke the device and pressed ‘Make my life easier’

Related posts:

  1. How to Backup Your SHSH Blobs Using Firmware Umbrella [Mac]
  2. How to Backup Your SHSH Blobs Using Firmware Umbrella [Windows]
  3. How To Downgrade Your iPhone From iOS 4.0.2 to iOS 4.0.1/iOS4 Without SHSH Blobs [Windows]
  4. TinyUmbrella: Save Your iOS 4 SHSH Regardless Of Whether Your iOS Device Is Jailbroken
  5. AutoSHSH : iH8Sn0w Releases AutoSHSH to Grab SHSH blobs for 3.1.3 and iPad 3.2

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