The recently released iOS 4.3.1 firmware update for the iPhone, iPad, and iPod Touch has successfully been jailbroken courtesy of some work by DjayB6 on the iOS 4.3.1 jailbreak bundle and Universal Ramdisk Fever. The jailbreak as of right now is only tethered for now, which means that you will have to boot it into a jailbroken state every time you reboot. Support for the iPhone 3GS and iPod Touch’s are on the way. Just follow the instructions below to jailbreak iOS 4.3.1 on the iPhone 4 using a combination of PwnageTool 4.2, Universal Ramdisk Fixer and the tethered boot utility. Here’s what you will need: PwnageTool 4.2 iOS 4.3.1 firmware iTunes 10.2.1 Mac OS X PwnageTool bundle for iOS 4.3.1 Universal Ramdisk Fixer tetheredboot utility Note: There is currently no unlock for the new baseband on iOS 4.3.1. If your iPhone relies on a carrier unlock, DO NOT update to stock iOS 4.3.1. iPad 2 users on iOS 4.3 should stay away from iOS 4.3.1 until further confirmation. Cydia is fully functional on iOS 4.3.1 It’s a semi-tethered jailbreak. Your baseband will not be upgraded during the restore process. Hacktivation is supported. Modifying PwnageTool Step 1: Download the PwnageTool bundle (includes Universal Ramdisk Fixer) for your version of iOS device. Extract the .zip folder, in there you will find a .bundle file, for this guide, we are using the iPhone 4 bundle iPhone3,1_4.3.1_8G4.bundle. Move this file to your desktop. Step 2: Download PwnageTool 4.2 and copy it to / Applications directory. Right click, and then click on “Show Package Contents” Step 3: Navigate to Contents/Resources/FirmwareBundles/ and paste iPhone3,1_4.3.1_8G4.bundle file in this location. Creating Custom Ramdisk for iOS 4.3.1 Custom Firmware Step 4: Download Universal Ramdisk Fixer (part of the PwnageTool bundle package that you downloaded in Step 1 above) and simply install it as shown in the screenshots below. This step is important because Ramdisk in the current version of PwnageTool is broken. This Universal Ramdisk Fixer basically patches it correctly for iOS 4.3.1 firmware. Building iOS 4.3.1 Custom Firmware Step 5: Download iOS 4.3.1 firmware and move the file to your desktop. Step 6: Start PwnageTool in “Expert mode” and select your device: Step 7: Click the “Browse for IPSW…” button and then select the correct firmware that you downloaded before: Step 8: Select “Build” to start creating custom 4.3.1 firmware file: Step 9: At this point PwnageTool will now create the custom .ipsw file for your iPhone which will be jailbroken. Step 10: Now follow the following steps to enter DFU mode using PwnageTool: Hold Power and Home buttons for 10 seconds Now release the Power button but continue holding the Home button for 10 more seconds You device should now be in DFU mode Restore iOS 4.3.1 Custom Firmware Using iTunes Step 11: Start iTunes, click on your iOS device icon from the sidebar in iTunes. Now press and hold left “alt” (option) button on Mac, or Left “Shift” button if you are on Windows on the keyboard and then click on “Restore” (Do Not press “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 custom firmware 4.3.1 file. Select the required custom .ipsw file that you created above, and click on “Open”. Step 12: iTunes will not do all the work and all you have to do is sit back and relax. This procedure involves a series of automated steps and all you need to do is be patient and not do anything silly. Just wait until iTunes installs the new firmware iOS 4.3.1 on your iOS device. Your iOS device screen at this point will be showing a progress bar indicating the installation progress. After the installation is done, your iOS device will be jailbroken on iOS 4.3.1. Booting in Tethered Mode Last but not the least, since there is no untethered jailbreak for iOS 4.3.1 yet, we will have to boot it into a tethered jailbroken state. To do this, we will make use of a utility named “tetheredboot” as shown in the steps below. Step 13: Download tetheredboot.zip utility for Mac OS X and extract the .zip file. Step 14: First, we will need two files from the custom iOS 4.3.1 firmware namely: kernelcache.release.n90 and iBSS.n90ap.RELEASE.dfu. To do this, make a copy of your custom iOS 4.3.1 file that you created above, change the extension of this file from .ipsw to .zip, and then extract this .zip file. Now copy kernelcache.release.n90 file, and then copy iBSS.n90ap.RELEASE.dfu files which are found under /Firmware/dfu/. Move all these files, and tetheredboot utility to a new folder named “tetheredboot” on the desktop. Step 15: Turn off your iOS device, and start Terminal on OS X and run the following commands: sudo -s enter your administrator password, then: /Users/MGN/Downloads/tetheredboot/tetheredboot/Users/MGN/Downloads/tetheredboot/iBSS.n90ap.RELEASE.dfu/Users/MGN/Downloads/tetheredboot/kernelcache.release.n90 (You will have to of course replace “MGN” with the name of the directory on your computer) Now press enter. NOTE: If the above fails, try ‘tetheredboot -i ibss -k kernel’ instead of ‘tetheredboot ibss kernel’: /Users/MGN/Downloads/tetheredboot/tetheredboot –i/Users/MGN/Downloads/tetheredboot/iBSS.n90ap.RELEASE.dfu -k/Users/MGN/Downloads/tetheredboot/kernelcache.release.n90 Tip: Simply drag and drop in Terminal – tetheredboot file, then iBSS file and then kernelcache.release file. You should now see some code running in the Terminal window, at some point, it will ask you to enter DFU mode. Now follow the following steps to enter DFU mode: Hold Power and Home buttons for 10 seconds Now release the Power button but continue holding the Home button for 10 more seconds You device should now be in DFU mode Now wait for your device to boot, Terminal at this point will be showing “Exiting libpois0n” message. After a short while, your iPhone, iPad or iPod touch will be booted in a jailbroken tethered mode! 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