Notcom the creator of TinyUmbrella has finally cleared up a lot of misinterpretation regarding out of the box iphone’s with 4.0.2 firmware being able to downgrade. As you may know a lot of people are posting a how to guide on downgrading to 4.0.1 without shsh’s. Sorry to all but that is completely false.

Notcom explains it all on his blog and then some telling people what exactly is being done when doing this supposed firmware trick that lets you downgrade. More info after the break:

Below is what NotCom had to say about this whole situation:

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.

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’

That’s it folks. Sorry to be a buzzkill but there was much confusion about this issue and many blog posts that simply didn’t give the full story of what exactly was going on.

Now that we have the iphone 4 jailbreak along with it being an untethered jailbreak for all other i-devices it is very important for yout to save your shsh blobs. A lot of new people in the jailbreak scene don’t know what those are and its ok you don’t need to just save them. If your not jailbroken I recommend saving your shsh’s anyway so that if you ever want to jailbreak you can. This is urgent right now it is rumored a firmware update is coming today!

Your probably wondering what is all this shsh stuff. Basically whenever Apple releases a new firmware update for i-devices it doesn’t allow you to downgrade to old firmware versions. If you update to a new firmware and there is no jailbreak for it your stuck without, unless you have your shsh’s save. With your shsh’s saved you can downgrade to the old firmware version that is jailbreakable. Enough talk here is how to save shsh’s so get them whether your jailbroken or not:

• Visit http://thefirmwareumbrella.blogspot.com/
• On right hand side choose and download either windows or osx program
• Open TinyUmbrella and you will get a screen like the one above, click save my shsh
• Your done now hang tight and DO NOT update your i-device when the new firmware drops.

via iphonespot

Now that Apple has released the 4.1 iOS beta you should all know to back up our shsh’s locally and on sauriks server by using a program called TinyUmbrella. Saving your shsh’s is a back up plan just in case you upgrade to Apple’s latest firmware that isn’t jailbreakable, the shsh’s allow you to sign your own firmware and downgrade to a jailbreakable firmware. Lets not get too complicated just do the following:

• Visit: http://thefirmwareumbrella.blogspot.com/
• On the right you’ll see quick links
• Download the program for your OS
• Have your i-device connected, run program and click save my shsh
• To be more cautious click advanced options and by location choose Apple and save shsh locally, now you have two backups
• Now chill out and go on about your day.

via theiphonespot