Apple just released iOS 5.1.1 incremental Software update bringing minor improvements over 5.1 and fixing minor bugs. If you have inadvertently upgraded to iOS 5.1.1 and want to revert to 5.1 for any reason, follow the tutorial listed below that will guide you in detail about how to downgrade iOS 5.1.1 to 5.1. But yes, it will only work if you have already saved SHSH blob files for 5.1 firmware.

Saving SHSH files is bit cumbersome or rather tricky in iOS 5.x as it accommodates a new mechanism ‘APTickets’. You can use iFaith or redsn0w to do so. I find redsn0w as a convenient way to backup SHSH blob for my iPod touch 4G, iPad G, and iPhone 4.

Disclaimer: The steps listed below will work only on a Mac OS X. Many users are facing issues while downgrading from iOS 5.1.1 to 5.1 using Redsn0w on a Windows PC. In that case, it is advisable to use Sn0wbreeze.

Note: This method will not work for iPad 2, The New iPad (iPad 3) or iPhone 4S. You can downgrade from iOS 5.x to iOS 4.x (however, you must have saved SHSH blobs for iOS 4.x) but you cannot downgrade between versions of iOS 5.x (for instance, iOS 5.1.1 to iOS 5.1).

Requirements:

  1. You must have both the hash file and APTicket file saved for 5.1 for your iDevice.
  2. Download the 5.1 IPSW for your iDevice (to desktop).
  3. Download the latest version of Redsn0w tool (to desktop).

Downgrade iOS 5.1.1 to 5.1 Instructions (Mac Only):

STEP 1: If you require a No_BB IPSW to preserve your baseband for unlocking, you must use Redsn0w to construct that prior to stitching your hashes/APTicket to the IPSW.

STEP 2: You must retrieve your saved hash file from your computer. TinyUmbrella hides the default folder in which the hash files are saved (/Users/your-user-name/.shsh)

  • To un-hide these, enter the following into the Terminal app on Mac.

defaults write com.apple.Finder AppleShowAllFiles YES

  • Then hold down the Option key and right click the Finder icon.
  • Re-launch the Finder.
  • Browse to /Users/your-user-name/.shsh and copy (not move) the “1033310xxxxxxiphone3,1-5.1.shsh” file to desktop.

Note: The file name will vary depending on iPhone model and ECID # but should end in -5.1.shsh.

STEP 3: Once you have the hash file copied to the desktop, re-hide the folders/files by entering the following command into the Terminal app.

defaults write com.apple.Finder AppleShowAllFiles NO

STEP 4: Hold down the Option key and right click the Finder icon, re-launch the Finder.

STEP 5: Use Redsn0w to verify if the hash file is complete and valid.

  • Open Redsn0w; click Extras-SHSH Blobs-Verify.

  • If both the hash file and APTicket are saved, Redsn0w will display a verification like this:

STEP 6: Once you have verified your hash file, Open Redsn0w to Extras-SHSH Blobs-Stitch.

STEP 7: To identify your IPSW to Redsn0w, enter the iOS firmware you signed SHSH with and save the APTicket.

STEP 8: Click ‘Local’ button and then specify the file SHSH.plist previously created. This will identify your hash file to Redsn0w.

STEP 9: Allow Redsn0w to build the IPSW with stitched hash/APTicket file. It will start loading kernel cache and stitching the blobs. It will automatically add APTickets, patch iBSS and iBEC in the background.

STEP 10: When it is complete, Redsn0w will display a verification saying –’Blob stitching done’. Your iOS 5.x personalized firmware is created and available on your computer. The windows will display the path of the customized IPSW. This custom IPSW can be used with iTunes and TinyUmbrella to restore iOS device to iOS 5.1.

STEP 11: Put your iDevice in pwned DFU using Redsn0w and use iTunes to browse to this IPSW to restore to 5.1. To do so, launch the Redsn0w and go to “Extras” menu and then “Pwned DFU”.

Place your iDevice in DFU mode and then click on Pwned DFU. Launch iTunes then simply indicate the firmware created earlier (with signed and APTicket SHSH). Click ALT (keyboard) + Restore button (iTunes)

Note: Be sure ‘#’ is added in front 74.208.10.249 gs.apple.com in your host file.

If you get an error -1 at the completion, use Redsn0w Fix Recovery to kick it out.

You have now successfully downgraded your firmware from iOS 5.1.1 to 5.1 on Mac. For any issue, sound-off in the comment section below.

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