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So I wanted to jailbreak my iPhone and I was interested in it before but I never really took the time to. Research properly. Forgetting that I might jailbreak in the future, I updated my phone to iOS 9. I didn't really like iOS 9 and the fact that you can run a jailbreak on it.

I researched a little and found out that I can restore with an IPSW file and I was stoked. However, it seems that Apple only “signs” down to ios 8.4.1, an UN-jailbreak able version of iOS.

What does it mean if an IPSW file is not signed? And what would happen if I were to put an unsigned version of iOS on my phone?

I got the IPSW file from this website. I have tried researching pretty much everywhere but I cannot find an answer.

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4 Answers 4

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Easily spoken, you could say ipsw files are not complete. They're missing that so-called signature. It's like a contract; it has no value without the signature. Every time you install new firmware on the iPhone, iTunes calls to the Apple servers and ask for that approval signature. For numerous reasons, Apple doesn't give out those signatures for older firmware versions.

There's not much you can do. The only thing you can do is downgrading to 8.4.1 and hope one day somebody releases the jailbreak for it. But for now, you're stucked.

UPDATE: As of Oct 2015 Apple stopped signing 8.x. As of Oct 2016 Apple stopped signing 9.x. While this answer is not correct any more it still describes the general idea behind Apple firmware signing.

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You can obtain a signature which developer ID, and Date Signed. if you know what the orignal checkSum is it is easily modified using notepad and fiddler 4. For file signatures, push a Untampered IOS Update through 3utools, Flashing with proFlash. Before starting the process, have fiddler 4 open and then start the flashing. during the process fiddler will recieve a response for the ios update md5 checksum from its servers, and the file signature files later on. Once complet to find the signature go into the 3uTools system files, and inside the Other folder you will find a zip file call ss_ios.zip . Inside that zip you will find a .sig file. that is the file you must use to sign your modded files. Also If the Last Modified Date doesnt match the original file, you will also fail. Though changing the metadata on the last modified date is easy.

Another note if the crc32 value doesn't match, the buildManifest or the device tree information for that file. you will also fail.

Apple uses md5 as an initial check, then crc32, date modified, File Signature. If any fail the image is reversed from disk, and the old image is restored to last state.

Hope this help you out!!

USE 3uTools to push the ios. in Itunes if your md5 checksum value isnt write then it says ipsw not signed. FYI

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    They still sign for IOS 9.x As long as that is the highest the device can Go. I personally have a Modded IOS 9.3.5 That i created. Bypass All Security measures is a beast but if you take your time and do it correctly you can bypass them.
    – Michael Smith
    Dec 2, 2017 at 1:03
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The above answers are right...that if the ipsw is signed you can install (flash) it through iTunes (PC/MAC) and the unsigned ipsw can't be install with iTunes

But if you are a Obstinate Person and still want to downgrade your ios version....then download the wished ipsw firmware from here--> http://ipsw.me and install (flash) with 3u tool....download from here--> http://www.3u.com enter image description here

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    you sure it is possible to downgrade from say 14 to 12?
    – mjs
    Nov 5, 2020 at 13:24
  • I don't think it's actually possible
    – 118218
    Jan 31, 2021 at 9:39
  • @mmm, did you try it?
    – 118218
    Jan 31, 2021 at 9:40
  • no it is not ...
    – mjs
    Jan 31, 2021 at 15:47
  • the link it's broken, the program can't be downloaded
    – Enrique San Martín
    Jun 6, 2021 at 16:50
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iOS won't run unless Apple signs the IPSW.

So, unless you get Apple to sign the software in and save a copy of that signed certificate, you can't use that IPSW now that the window to get Apple to sign it has passed.

Sort of a sad trombone, game over situation.

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    “That sucks, if I buy a product, I would like some sort of control over the software.” You don’t if you buy an iOS device which is not a new concept. And Apple does not support Jailbreaking.
    – Giacomo1968
    Sep 27, 2015 at 17:06
  • @VishvakSeenichamy you have control, but you do need to research how things work and educate yourself. This isn't something new for iOS 9 - see the questions here on rolling back an update. You have hours to do so typically and not days or weeks.
    – bmike ♦
    Sep 27, 2015 at 22:17
  • @VishvakSeenichamy You should have read EULA before buying the iDevice.
    – Pratik
    Sep 28, 2015 at 1:42

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