xzKinGzxBuRnzx

Apple released OS 3.1.3 very unexpectedly, OS 3.1.3 for iPhone 3GS is incompatible to jailbreak with redsn0w/pwnage tool/sn0wbreeze. So as of today, Apple has stopped signing 3.1.2 restore files. That means that if you have a 3GS iPhone you cannot restore any firmware other than 3.13. If you guys updated to 3.1.3 and wanna get back to OS 3.1.2 or below here is the step by step guide to downgrade your iPhone OS 3.1.3 to 3.1.2 or below. This hack is useful only for those peoples who saved their SHSH to Cydia Server before the release of OS 3.1.3 via Cydia “make my life easier” button.

The process is very simple all you have to do is to add Saurik’s Server address to your system hosts file. This trick make iTunes thinks it is talking to Apple, it is talking to Cydia instead while the restoring process. Doing this will allow iTunes to access signatures already stored by Cydia “on file” feature. In simple words this duplicates the functionality exposed by Apple’s signature server, except using “on file” results rather than live request.

Note:
1. This process is only for those who saved their SHSH to Cydia Server already.
2. Don’t use this procedure for 3.0.1, because Saurik Server do not have signatures for 3.0.1
3. Read the process and Saurik post two-three times before starting the process.
4. iPhone unlockers note that by doing this you can downgrade your firmware only, your baseband is still at 05.12.01 which is un-hacked at the moment.


Part 1:

How to Edit and Save Hosts file in Windows
Open Notepad with Administrative privileges by clicking Start, All Programs, Accessories, and then right-click Notepad and select to open as Administrator.
Now that Notepad is open with Administrative privileges browse to (C:\Windows\System32\drivers\etc\) in Notepad and open the hosts file, and add the following entry to the bottom of the file.


Note:
If you do not see the hosts file, please be sure to select all files as seen in the picture below. If that doesn't work then you can also access this file by typing this into run (C:\Windows\System32\drivers\etc\hosts)



Now you navigate to files menu and save the hosts file. By doing this you changed the communication server, and then we will ensure that iTunes checks the firmware on the server rather than opens Saurik toApple! Because your ECID is on that server, the verification will fail and restore the previous version will be done without too many problems!


How to Edit and Save Hosts file in Mac OS X
Navigate to /etc and look for hosts file, right click on hosts file and open with Text Edit, and add the following entry to the bottom of the file.


Now save the file and click on Save As.
Because Text Editor can’t save your system files, here comes the tricky part, in save as windows use the following settings. Or take a close look at the following image.

In Where locate to Desktop
Uncheck the “ If no extension is provide, use .txt “ and then press the save button.




A host file will be appear on your Desktop, just drag and drop to /etc and follow the onscreen instructions.



Press the Replace and enter your Password



By doing this you changed the communication server, and then we will ensure that iTunes checks the firmware on the server rather than opens Saurik to Apple! Because your ECID is on that server, the verification will fail and restore the previous version will be done without too many problems!

Part 2:

Now you can do your Normal Restore to 3.1.3 (with Recovery Mode) and Downgrading from 3.1.3 to 3.1.2 or below (with DFU Mode) as usual.

To Downgrade iPhone 3GS from 3.1.3 to 3.1.2 or below:
1. Connect your iPhone to your computer
2. Turn iPhone off.
3. Hold power and home together for 10 seconds (exactly).
4. Release power but keep holding home until the computers beeps (observed on a PC) as a USB device is recognized.
5. A few seconds later iTunes should detect your iPhone.

Note:
If the Restore Logo is present on the screen, you are in Recovery Mode, not DFU.

Once your iPhone is in DFU mode following message will be appeared in iTunes. Click on “OK”, Now hold shift key while clicking Restore in iTunes and browse the OS you wish to restore to your iPhone 3GS. Now the restore process will take 10 – 15 minutes. Thats it your done, you may now enjoy your downgraded OS.


Note:
If you encountered error message like 1601, 1602, 1600 or anything else then try putting the iPhone into DFU mode and try again or check to make sure your hosts file is correct and that you did have SHSH's on file on Cydia for the OS your attempting to restore to.

You can download the firmware from here

--Some images was used from ihackintosh.com Source

paradise2418

hey, i follow your instruction, but all i got from itune when the 3.1.2 restore file done extracting and verifying, "not eligible for this build"
didnt get any other error msg.
does that mean , i didnt do the host file correctly, or i didnt store my shsh on cydin or saurik server?
I did do the exact thing to my host on my mac.
My iphone is 3gs 16GB 3.1.2/5.11.07 originally, bought it 1 month ago. and jailbreak it successfully with blackrain,
after a crash, stupidly enough to restore on itune, and u all know that now my iphone is running on 3.1.3/5.12.01.
i heard so many ppl could downgrade with their previous shsh file saved.
since i forgot if i save it, i dunt know if the msg not eligible mean unsaved shsh.
plz help me on that,
gary2430@hotmail.com

xzKinGzxBuRnzx

Make sure your device is in DFU mode not recovery mode. Then make sure you've got the hosts file correct. If that doesn't work try only putting this in the hosts file, no #

and of course make sure you have a shsh on file on cydia, that required you to hit the make my life easier while you was on 3.1.2 with cydia open.

if you had iTunes open while editing the hosts file, perhaps reopening it or even a restarting your pc. I just tested it though and it does work...your messing up somewheres.

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biker4life

hello

does this also work with the 3.1(7C144) Version? I ran blackra1n(rc3) and the first time i used Cydia on my iphone 3gs(3.1), i backed up my SHSH. Last week it crashed a few times and i found this How-To. I edited my Hosts file, and made a Ping to gs.apple.com and i get a reply from 74.208.10.249(sauriks server). The i set my phone to DFU Mode but when i try to Restore an 3.1.2 or 3.1 in ITunes(Version 9.0.3.15) i get the error "not eligible for this build"
Pherhaps its a useful information for this problem: Sadly i have a newer iphone 3gs with the new bootrom

would be very happy if you could help me

xzKinGzxBuRnzx

Read above, this is most likely caused by not entering DFU mode or perhaps you didn't edit the hosts file correctly.

biker4life

Hey, thanks for your hints but i've checked everything multiple times. I tried it on 2 PCs, one is running Win XP SP3 x86, the second is running win 7 Professional x64. On both PCs i edited the host file correctly and when i do a ping to gs.apple.com i actualy ping the ip from sauriks server.
And i've always tried to get the 3.1 on my iphone, while i was in DFU Mode (I have a COMPLETLY BLACK Iphone Screen) and Itunes tells me that it has found an IPhone but when i try to restore the 3.1 or the 3.1.2 i get the error that it's not eligible.
I have also tried it with ITunes 9.0.2 but sadly it didn't work .

Any Idea what to do next?

xzKinGzxBuRnzx

You most likely don't have a SHSH on the Cydia server for that OS your trying to restore to.

Bubblemint

Hi New poster here,

Total computer noob to boot. I have downlaoded the firmware via the link in the OP, put my phone (3gs into dfu) , clicked ok to itunes knowing that there is a phone in recovery that needs restoring, held shift and clicked restore...

Now I hit the skids. Although I see the file on my desktop, itunes is not finding a file to download from.

What am I doing wrong ?

Copertus

I am having error 1015, any clue?
Thanks.