Downgrade iOS 4.3.4 to 4.3.3, 4.3.2, 4.3.1, 4.3, on iPhone 4, 3GS, iPad 2, iPad, iPod touch

Case : 아이폰 4.3.3 탈옥에서 수정복구 과정에서 무한루프 문제가 발생하여 4.3.4 업그레이드 진행하였음
           - 4.3.4 기능개선 여부 확인 불가
           - 순정에서 여러가지 불편한 사항 발생으로 4.3.3 다운그레이드 시도
           - SHSH 파일 백업이 존재함에도 불구하고 무한루프 발생 (Err Code : 1013)

Solution : 참고사이트

1. 아래의 방법으로 Step 1 ~ 5번까지 진행을 하였음에도 불구하고 1013 에러가 계속 발생하는 상황이라면....
   - Step 5에서 아이폰 화면에서 Dos Command같은 창으로 무수하게 많은 라인이 흘러간 이후에도....

2. Step4, Step5 의 아이튠즈를 이용한 복구, “Exit Recovery” 를 계속 반복하면 된다.
   - 본인의 경우 약 3회 수행 후 정상 다운그레이드 성공
   - 실패 후 아이튠스 복구+업그레이드를 통한 4.3.4 업그레이드 후 다시 시도하는 과정에서 많은 시간이 소요되었으나
      같은 방법을 수회 수행 후 완료됨
  
* 아이폰 USB 연결화면에서 DFU 모드 진입 방법 *
   1. USB연결화면에서 상담의 홀드버튼 약 5초 유지 : USB 연결화면 꺼짐
   2. 아이폰의 홀드 + 홈버튼 약 10초 유지 : USB연결화면이 나왔다가 사라지더라도 10초이상 유지
   3. 아이폰의 홀드버트을 때고 약 20초 유지 : Tinyumbrella Log 탭에서 연결성공 로그 확인
   4. 아이튠즈를 이용한 "Shift + 복구"




[Step 1] 펌웨어 다운로드
 >>>> ISO 다운드레이드 펌웨어 다운로드

Download the required IPSW file to which you want to downgrade to, the links are given below for your convenience:

• iOS 4.3.3
• iOS 4.3.2
• iOS 4.3.1
• iOS 4.3

[Step 2] 아이폰 복구(DFU) 모드 준비
 >>>> 전원OFF > 아이튠즈 실행 > 파워버튼+홈버튼 > 파워버튼 = 복구모드

Once you’ve downloaded the required IPSW file, its time you put your iPhone, iPad or iPod touch into DFU mode.
The steps are as follows:

• Connect your iPhone, iPad or iPod touch to your PC or Mac.
• Turn your device off.
• Now launch iTunes.
• Hold down the Power button and the Home button simultaneously for 10 seconds.
• After 10 seconds, release the Power button but don’t let go of the Home button, your computer should detect a new USB device.
• At this point, iTunes will also recognize your device, whether its an iPhone, iPad or iPod touch.

At this point, your device’s screen should be off, if that’s so, then you’ve successfully put your device in DFU mode. If iTunes logo shows up, you’re in Recovery Mode, NOT DFU mode.

[Step 3] Host 파일 수정 (Apple Domain-Name)
 >>>> C:\Windows\System32\drivers\etc\Hosts에 "74.208.105.171 gs.apple.com" 추가

Here comes the tricky and the most important part, you’re going to fool iTunes into thinking that its in contact with Apple’s servers, whereas we’re going to change that to Saurik’s server.
In order to do this, follow the steps given below:

Windows users:

Navigate to C:\Windows\System32\drivers\etc\ and locate the file named as “hosts”.

Mac users:

Mac users can access the “hosts” file by navigating to “/etc/” folder, which can be found through Go > Go to Folder from within Finder.

If you’re on Windows, then open the “hosts” file in Notepad. If on a Mac, then open the “hosts” file in TextEdit, and add the following line at the end:

74.208.105.171 gs.apple.com

Refer to the screenshot below if you’re having confusion:

Just save the file and close Notepad or TextEdit, and you’re all set for the downgrade.

A quick note for Windows 7 and Vista users: Start Notepad with “Administrator privileges”, that can be done by right-clicking the Notepad app, and there you will see the “Administrator privileges” option, simply click and launch.

A quick note for Mac OS X users: While saving the host file on your Mac, you should have complete read and write privileges in order to make changes. Getting a permission error? A simple workaround is to copy the host file to your Mac’s desktop, from there make the changes in TextEdit, save the file, and copy it back to the original location, and replace the original host file with the one which you just created.

[Step 4] 아이튠스를 통한 복구
 >>>> 아이튠즈 > Shift + 복구 > 복구 도중 Error 발생하면 Step 5 진행

Launch iTunes, choose your device from the left sidebar. Hold down the left “Shift” key if you’re on Windows or hold down the left “alt” key if you’re on a Mac and click on “Restore”, do not click anything else! A new window will pop up asking you for the location of the IPSW file.

Navigate to the desired firmware to which you want to downgrade to, in this case it can be either iOS 4.3.3, 4.3.2, 4.3.1, 4.3 or 4.2.1. Once you find the required IPSW file, click “Open” and let iTunes do its thing.

In a matter of few minutes, iTunes will install the version of iOS which you directed it to install. At this point you should see a progress bar on your device, everything is automated, therefore don’t do anything silly. Your device will reboot automatically when everything is done.

In some cases, iTunes will throw 1013 error, ignore it, its perfectly normal when downgrading. At this point, your device will be in Recovery Mode with your desired version of iOS fully installed.

You should see a screen like the one below:

Its quite simple to get out of Recovery Mode, simply down this nifty program called TinyUmbrella (Windows, Mac) along with Fix Recovery (Windows, Mac).

[Step 5] TinyUmbrella 를 이용한 Exit Recovery
 >>>> TinyUmbrella 실행 후  "Exit Recovery" 클릭

Once you’re done downloading TinyUmbrella, launch it, and then click on the “Exit Recovery” button. In a matter of seconds, your device will boot up normally.

[Step 6] Host 파일 수정 (Apple Domain-Name 제거)
 >>>> 다운그레이드 완료 후 Hosts 파일 내 추가한 내용 삭제

Once you’re done with this, the last thing you’re going to do is remove the line you added to the “host” file in step 3, which is 74.208.105.171 gs.apple.com in order to receive updates from Apple’s servers normally.