There is much discussion on many blogs about a potential means of downgrading iOS 4.0.2 to 4.0.1 by simply changing a couple values in the buildmanifest.plist and copying all of the images from 4.0.1 into 4.0.2 and then deleting the files ending with 002. Following all of this, perform a DFU restore and somehow you will be on 4.0.1.
There is a perfectly logical explanation for all of this and I will lay out exactly what is happening and explain why it is working for the folks that are the lucky ones.
Let me get this out first.
- This is not a miracle, at least not in the sense you all hope for
- SHSHs are STILL required for any iPhone 4, iPhone 3GS, iPad, iPod Touch 3G, and iPod Touch 2G (MC Model)
- There is NO way around this... unfortunately this method included.
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'