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Does Pwned DFU mode allow an iPhone 4 to install any version of iOS?

I have read

and watched

Then I come up with a question: Since Pwned DFU mode allows the iPhone to download an customized ipsw created from sn0wbreeze, does it mean that Pwned DFU mode allow an iPhone 4 to install(upgrade or downgrade) any version of offical iOS without requiring an SHSH blob for the corresponding iOS?

A screenshot to show the ipsw difference, using iPhone 4 ipsw with sn0wbreeze Simple Mode.

enter image description here

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    AFAIK, you still need an SHSH blob for the corresponding iOS. For example, if you have blobs for 4.1.1 and 4.2.1, you can install those iOS versions, but you can't install any other ones. Of course, you can always install the latest version of iOS, regardless of SHSH blobs. – Faiz Saleem Mar 9 '13 at 14:05
  • If it is truth that I can always install the latest iOS but not older ones, it means that I still need SHSH blobs of the latest iOS for my iDevice, except that I fetch them on the fly from Apple server. – Jimm Chen Mar 10 '13 at 17:29
  • Sorry, I would rather refrain from that. I hope some one can point out the key difference between a sn0wbreeze-crafted ipsw and an older-version iOS official ipsw that results in flash-able/non-flash-able result by iPhone 4. – Jimm Chen Sep 13 '13 at 7:32
  • @JimmChen Old question, I know, but people getting here should know that I have a definitive answer to yours and many other people's questions about unorthodox upgrading/downgrading here: apple.stackexchange.com/a/114076/18387 – Andrew Larsson Mar 2 '14 at 23:36
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You need those SHSH blobs. I've tried almost anything else available online, without success. Updating to the latest version via restore (without the blobs) is no problem ofcourse.

When you jailbreak your device it will store the SHSH blob on Cydia server, as you can fetch them from their servers with your current device UID if lost.

A SHSH blob is a small piece of data with Apple's signature connected to your device ID. Since you can only validate iOS versions with your own device ID, there's currently no way to install previous versions without having "your" blob.

Good luck!

  • Thank you for your comment. But I hope someone can explain why it is the case. What is the key difference between a customized ipsw and an outdated ipsw ? On the other hand, do you mean if I have saved specific SHSH blobs for iOS 5.1, I will be able to restore to 5.1? -- but sn0wbreeze's simple mode does not seem to ask the user where to find the .shsh file. – Jimm Chen Mar 10 '13 at 17:32
  • I think your blobs back to iOS 3.1 is saved on Cydia's server(some piece of software did this for you automatically), so you must have Internet access to fetch them before you can see them listed in TinyUmbrella or like. – Jimm Chen Mar 11 '13 at 0:44

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