There’s a lot of confusion about the SHSH blobs, and once saved ( see tutorial here and here ), how can we use them to downgrade our iOS devices. The problem is, that iOS devices have to communicate with Apple’s servers before allowing the installation of any version of firmware (restore or update ) .With the release of Firmware 3.1.3, Apple’s server has stopped certifying all previous firmware and this makes it impossible to restore your device to a previous release. The certification is done through 3 files called IBSS, IBEC and ECID that, once signed, they are a kind of “green light” to install the firmware through iTunes.
IBSS and IBEC files are generated during a firmware restore in iTunes and placed into a temporary folder on your computer. You will have no problem on retrieving this files, but the missing piece of this puzzle is the ECID file that Apple doesn’t allow you to retrieve.
NOTE: there is no issue downgrading an iPhone 2G/3G or 1st gen/2nd gen iPod Touch to FW 3.x even from 4.x even with iTunes 9.2+ . Only restores of iOS 4.0 itself are limited by Apple on these devices
1. Load a Terminal shell
2. Type: sudo /Applications/TextEdit.app/Contents/MacOS/TextEdit /etc/hosts . You will be prompted to type-in your Mac’s password.
3. This will open the exact file you’ll need to edit. Ignore the first entry with the #127.0.0.1 gs.apple.com UNLESS it doesn’t have the #. It needs to be there or simply delete that line (the # signifies that it’s a Remark. Make sure that you have the 126.96.36.199 gs.apple.com entry and that it doesn’t have the #. Click on File / Save and reboot.
4. Connect your iPhone, load iTunes and alt+restore. Now browse for the .ipsw, and restore your iPhone.
1. Click on the Start Orb and type “notepad” without the quotes. Right click on notepad and the Run as Administrator
2. Click on File / Open /Browse. Open your C drive, drill down to Windows\System32\Drivers\Etc. Change the criteria from Text Documents to All Files
3. You’ll probably have something similar to the following image. Ignore the first entry with the #127.0.0.1 gs.apple.com UNLESS it doesn’t have the #. It needs to be there or simply delete that line (the # signifies that it’s a Remark. Make sure that you have the 188.8.131.52 gs.apple.com entry and that it doesn’t have the #. Click on File / Save and reboot.
4. Make sure that you reboot or else you’ll get a 3194 error from iTunes!
5. Connect you iPhone and open iTunes if it doesn’t auto load. Hold your left Shift key and click Restore and drill down to where you have the previous iOS firmware. Typically it’s located at C:\Users\%username%\AppData\Roaming\Apple Computer\iTunes\iPhone Software Updates. (replace %username% with your logon name)
6. When it’s down you’ll get a 1004 error. Just ignore.
7. Now open your Internet browser and go to http://thefirmwareumbrella.blogspot.com/.Under Quicklinks on the right hand side look for TinyUmbrella [WIN] and download.
8. Click on Kick Device Out of Recovery and that’s about it.
9. Look at your iPhone and it’ll be activated, yay!