Today Apple iOS 4.3.5 has just been released for iPhone, iPod Touch and iPad to fix a security issue with certificate validation issue. But if you accidentally updated your firmware to 4.3.5 and you had saved your SHSH blobs for iOS 4.3.4, 4.3.3, 4.3.2 or 4.3.1.
Geohot has the guide on how to downgrade from iOS 4.3.5 to any of iOS 4.3.4, 4.3.3, 4.3.2 or 4.3.1.
Just follow the step by step procedure here at Geohot's blog.
Here's the full guide on how to Downgrade iOS 4 iPhone 3GS, 3G and iPod touch to version 3.1.3 / 3.1.2
Maybe you upgrading to iOS 4 and been slowed down your mobile device and that you want to go back to iPhone 3.1.3 / 3.1.2. Or if you are one of those iPhone 3GS (new bootrom) or iPod touch 3G / 2G (MC model) user who has upgraded to iOS 4 only to find out that you cant jailbreak it can follow the instructions posted below to downgradeiOS 4.0 to iOS (formerly iPhone 3.1.3 or 3.1.2).
Hold Power and Home buttons together for 10 seconds or so.
Release Power button but keep holding the Home button until your computer recognizes a new USB device.
iTunes will now recognize your iPhone.
Note: Your iPhone screen at this time should be blank (black in color), if not, then you are most likely in Recovery Mode,not DFU mode. Step 3 is for iPhone 3GS users only.
If you are on iPhone 3G or iPod touch 2G (non-MC model), skipStep 3 and continue from Step 4)
Step 3: This step is applicable to iPhone 3GS, iPod touch 3G and iPod touch 2G (MC model) which have their SHSH blobs (ECID SHSH) saved on Cydia for the firmware you downgrading on. If you don’t have your SHSH files saved, you cannot downgrade the mentioned devices.
So what we will do is to trick iTunes into thinking that it is watching Apple servers, while in real, we are going to change the address to Saurik’s server.
Step 4:
Navigate to C:\Windows\System32\drivers\etc\ and locate “hosts” file. Step 5:
Mac users can get to “/etc/” directory by going through “Go –> Go to Folder” from Finder.
Step 6:
Open this “hosts” file in Notepad (for Windows) or TextEdit (for Mac OS X) and add this
74.208.105.171 gs.apple.com
line as shown in the screenshot below:
NOTE :
for Windows 7 and Vista: Start “Notepad” with Administrator privileges by right clicking on “Notepad” app, and click on “Run as Administrator“ option. Step 7:
You will now have to restoreyour iPhone or iPod touch to the firmware you downloaded in Step 1. Click on your phone icon from the sidebar in iTunes. Now press and hold left “alt” (option) button on Mac (Left “Shift” button on Windows) on the keyboard and then click on “Restore” (Not “Update” or “Check for Update”) button in the iTunes and then release this button.
This will make iTunes prompt you to select the location for your downloaded firmware file. Select that ipsw file and click on “Open”.
Step 8:
Now sit back and enjoy as iTunes does the rest for you. This will involve a series of automated steps. Be patient at this stage and don’t do anything silly. Just wait while iTunes installs firmware on your iPhone or iPod touch. Your iPhone screen at this point will be showing a progress bar indicating installation progress. Now at some point, iTunes will throw 1011, 1013 or 1015Errors see our posted here how to fix them. This is normal, just ignore this error as the firmware has already been successfully installed on the device.
Step 9:
Now you will need to exit your device from Recovery Mode. To do this, download a program called RecBoot (Windows / Mac). Run it and the click on “ExitRecovery Mode” button. Your device will now restart normally.
Remove the two Phillips #00 screws from the dock-connector end of the iPhone.
Step 2
Remove the metal handle from the suction cup. It's easier and safer to grip the suction cup's base instead of the metal handle.
Be very careful when opening the iPhone so that the cables under the display are not severed.
There is a rubber gasket between the silver front bezel and black display assembly. A bit of force is required in this step to separate the iPhone's display assembly.
Use a small suction cup near the Home button to gently pull up the bottom portion of the iPhone's display assembly.
Step 3
The display assembly is still connected to the iPhone by several cables, so don't try to remove it entirely just yet.
Rotate the display assembly up until it is at an angle of approximately 45 degrees.
Step 4
Continue to hold the display assembly with one hand, and use your other hand and a spudger to disconnect the black ribbon cable labeled "1."
Step 5
Rotate the display assembly up until it is roughly vertical. This will allow easier access for disconnecting the remaining cables.
Use a spudger to disconnect the black ribbon cable labeled "2."
Step 6
Use a spudger to flip up the black plastic tab holding the remaining ribbon cable in place. The black will rotate up 90 degrees, releasing the ribbon cable.
The plastic tab may be white (instead of black) on some iPhone models.
Slide the ribbon cable out of its connector, and remove the display assembly from the iPhone.
Step 7
Remove the single Phillips #00 screw from the corner of the display assembly.
Step 8
Remove the two Phillips #00 screws from the right side of the display assembly.
Step 9
Turn the display over, and carefully peel up the thin strip of black tape on the edge of the display assembly.
Keeping the tape from sticking to itself can be tricky. We recommend placing the tape on a wax-coated piece of paper (any sticker backing will do).
Step 10
Remove the three Phillips #00 screws from the left side of the display assembly.
Step 11
Carefully insert a metal spudger between the two metal rails along the edge of the display assembly. Gently rotate the spudger to lift the LCD up from the glass.
Step 12
Turn the display assembly over and again carefully insert a metal spudger between the two metal rails along the edge of the display assembly. Gently rotate the spudger to lift the LCD up from the glass.
Step 13
Separate the LCD and glass by sliding the LCD panel away from the ribbon cables on the glass.
Remove the two Phillips #00 screws from the dock-connector end of the iPhone.
Step 2
There is a rubber gasket between the silver front bezel and black display assembly. A bit of force is required in this step to separate the iPhone's display assembly.
Use a small suction cup near the Home button to gently pull up the bottom portion of the iPhone's display assembly.
Step 3
The display assembly is still connected to the iPhone by several cables, so don't try to remove it entirely just yet.
Rotate the display assembly up until it is at an angle of approximately 45 degrees.
Step 4
Continue to hold the display assembly with one hand, and use your other hand and a spudger to disconnect the black ribbon cable labeled "1."
Step 5
Rotate the display assembly up until it is roughly vertical. This will allow easier access for disconnecting the remaining cables.
Use a spudger to disconnect the black ribbon cable labeled "2."
Step 6
Some iPhone 3Gs may have the connector colors reversed (black plastic tab, white connector). Make sure you're flipping up the tab properly, otherwise you may damage the connector.
Use a spudger to flip up the white plastic tab holding the remaining ribbon cable in place. The white tab will rotate up 90 degrees, releasing the ribbon cable.
Slide the black ribbon cable out of its connector, and remove the display assembly from the iPhone.
Step 7
Insert your SIM eject tool or a paper clip into the hole next to the headphone jack.
Press down on the tool until the SIM card tray pops out.
Grasp the SIM card tray and slide it out of the iPhone.
Step 8
Use a spudger to disconnect the ribbon cable labeled "4."
Step 9
Use a spudger to disconnect the ribbon cable labeled "5."
Step 10
Use a spudger to disconnect the ribbon cable labeled "6."
If you have an iPhone 3GS, refer to picture 2 and use a spudger to disconnect the ribbon cable labeled "7."
Step 11
Carefully peel up the small sticker labeled "Do not remove."
Step 12
Remove the following 8 screws:
Five 2.3 mm Phillips #00 screws with partial threads securing the logic board to the rear panel.
Two 2.3 mm Phillips #00 screws with full threads securing the logic board and camera.
One 2.9 mm Phillips #00 screw from beneath the "Do not remove" sticker.
Step 13
Use a spudger to gently pry the camera up and out of its housing in the rear panel. The camera cannot be removed entirely yet because it's connected to the bottom of the logic board.
Step 14
Use a spudger to gently pry up the end of the logic board closest to the dock connector.
If the board won't lift up, double check to make sure all the screws securing the logic board have been removed.
Step 15
Slide the logic board towards the dock connector and out of the iPhone.
Step 16
Use a spudger to pry the battery up from the rear panel. The battery is attached with an adhesive strip around the perimeter of the battery. To prevent the battery from bending during the removal process, we recommend against using just the plastic pull-tab .
Just follow the step by step procedure here at Geohot's blog.
