[HOW TO] Downgrade Iphone 3Gs from 3.1.3 to 3.1.2 (with SHSH)
First off all Credit goes to Saurik & Reako.
Very important -
You must have your SHSH on file with saurik and have already edited your hosts file prior to this document. A simply google search will teach you how to edit the hosts file on Mac and Windows.
Bypassing the Overlord
To this end, I have constructed a server that duplicates the functionality exposed by Apple's signature server, except using "on file" results rather than live requests.
All we need, then, is to make iTunes use it. Luckily, most operating systems also have the ability to locally define bypasses on specific hostnames through a file called hosts. Using this, we can redirect requests to Apple's signature server to Cydia.
So, open the file C:\Windows\System32\drivers\etc\hosts (Windows) or /etc/hosts (Mac OS X) and add the following entry to the bottom of the file.
-First, connect your iPhone to the USB and put it into DFU mode. (if you don't know how to get into DFU mode, please google it). iTunes will display an alert stating you need to restore your device, click ok then hold option + click restore and navigate to your previously downloaded 3.1.2 FW.
- After the restore finishes you should be hit with a 1015 error. That's expected. Your phone should be in Recovery mode now and iTunes will tell you to restore again. Click ok then hold option + click on restore again - this time you do not have to go into DFU mode - and navigate to the 3.1.2 FW.
-After the restore finishes again it'll throw another 1015 error. That's expected again. This time, just select ok and close iTunes. Fire up redsn0w - make sure it's the 0.9.4 version - and jailbreak as normal.
-After the jailbreak is finalized your device should reboot and strange enough you successfuly downgraded to 3.1.2.
PLEASE NOTE: AFTER THE FIRST JAILBREAK YOUR DEVICE WILL NOT BE JAILBROKEN. Don't ask my why but for some reason all it does is properly finish the downgrade process.
Now, you are more than welcome to use your favorite jailbreak software (blackra1n or redsn0w) to re-run jailbreak process and once it's finished VOILA! You should be jailbroken on 3.1.2 WITH service!
How to downdrade iPhone 3gs 3.1.3 to 3.1.2
I would like to know how to downgrade my iPhone 3gs