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Thread: SHSH Blobs - General Question

  1. #1
    Default SHSH Blobs - General Question
    I always see references to backing up SHSH blobs, but I never see an explanation on what the heck they are and why/how to do it.

    First: What are SHSH blobs?

    Second: What is the benefit of backing them up?

    Third: How do I back them up?


    I have an iPhone 4 running 4.0.1. I haven't yet jailbroken it, but I probably will soon. I was just waiting for there to be ample reviews on the jailbreakme.com method before I took the plunge.

    I'm hoping to go get an iPhone 4 for my wife today, which will obviously already be updated to 4.0.2. Is there any way to restore it to 4.0.1 so it can be jailbroken too? If I back-up my SHSH blobs (whatever those are), would it be possible for me to use THAT to jailbreak my wife's 4.0.2 iPhone 4?

    TIA!

  2. #2
    Livin the iPhone Life jkmonkey's Avatar
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    This explains what they are:
    http://modmyi.com/forums/3g-s-downgr...an-saurik.html

    Use can use tiny umbrella to get them saved or hit the make my life easier button in cydia after your jailbroken.
    Last edited by jkmonkey; 2010-08-28 at 06:57 PM. Reason: Automerged Doublepost

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  4. #3
    Livin the iPhone Life
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    In order to restore a iPhone, it requires a signature file from Apple. These signature files come in the format of an SHSH file. Every time Apple releases a new firmware, they stop signing requests for the old firmware. For example, 4.0.2 was recently released, so now if you want to restore to 4.0.1, you send a request to Apple, but they deny it and you can't restore to that version.

    The benefit of backing up these SHSH files is that it allows you to restore to any firmware version that you have a file for. Apple has stopped signing 4.0.1 but if you made a copy of their signature while they were still being signed, you can use that now to trick the phone into thinking that the signature came from Apple and you're then allowed to downgrade.

    You can back them up by either going into Cydia and click the 'Make my life easier' button, which the SHSH files on Cydia, or by using TinyUmbrella to store them on your own computer.

    The jailbreakme.com jailbreak works fine and there's nothing to worry about.

    As for your final question, no, you will never be able to downgrade your wife's phone. You won't be able to downgrade your own phone either. The reason for that is that you can't get a signature for 4.0.1 because the current firmware on your phone doesn't matter. All that matters is what version Apple is signing, which is 4.0.2 at the moment. Also, the signatures are firmware version and device specific, meaning that one single SHSH file will only work for one specific phone and one specific firmware version, so even if you had your own 4.0.1 SHSH, it wouldn't work for any other phone than your own.
    We're all just toymakers in the game of life.

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  6. #4
    My iPhone is a Part of Me Trooper Sam's Avatar
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    SHSHs are signature files generated by Apple. These signatures are required in order to install ANY firmware on an iPhone 3GS or iPhone 4, and several other iDevices.

    Apple came up with this method in order to prevent users from installing older and jailbreakable firmware versions on their iDevices. Their method is to release a new firmware version, and then stop serving up the SHSH signature requests for the previous version. Once they stop signing that old version, no new requests for it will ever be fulfilled. And that means iTunes will tell you that your device isn't eligible for it.

    Here's the trick our team figured out: how iTunes asked for that signature, what it looked like, and how to save it for later and serve it up in the future on demand.

    By the way, each and every SHSH is unique to the individual device, tied to it by the device's unique ECID, or Exclusive Chip ID. SHSHs saved for one device are useless for an identical device, or different model, as the ECIDs are quite as nearly unique as fingerprints.

    So what does this all mean to you?

    Well, you say you've got an iPhone 4 with 4.0.1, and you're thinking about jailbreaking it. No problem, you CAN jailbreak it as it sits.

    However, if anything ever happens to it, it locks up, won't boot, seems like it's been bricked...you're unlikely to be able to put 4.0.1 back onto it again. And why?

    Because you never saved the 4.0.1 blobs, or SHSHs. Apple stopped signing 4.0.1 several days after it released 4.0.2, so you can't get that signature anymore. And therefore you can't save it to serve up to iTunes at a later date anymore.

    As to the iPhone 4 you wish to buy for your wife, that will come with 4.0.2? You already know that 4.0.2 is not able to be jailbroken, but your specific question was whether you can downgrade it to 4.0.1.

    The answer? Unlikely. The odds are poor that SHSHs have ever been saved for a brand new device, so there will be no downgrade path for it below 4.0.2.

    Notice that I have used the term unlikely, rather than impossible. I say that for both because in some instances, reported on this forum, people have found SHSHs saved for their devices, even though they were brand new. How this happened, nobody can seem to explain. But I do recommend checking, because the worst you can find out is that you have none saved, and then you're no worse off than you were before you checked.

    Good enough explanation to start?

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  8. #5
    How does one check if it's saved?

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  10. #6
    My iPhone is a Part of Me Trooper Sam's Avatar
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    - Download and run TinyUmbrella
    - Connect your iDevice
    - Click "Save my SHSH"
    - Check the "Advanced Options" box
    - Repeat for each eligible firmware version for your device

    The message window will tell you if they were successfully saved or not. If it says yes, then you can downgrade to that version you were attempting to save.

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    AUZambo (2010-08-29)

  12. #7
    Perfect explanations everyone. Thanks a ton!

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