Specifically for those wanting to jailbreak the iPad, the subject of SHSH blobs is one that you should get to understand.
SHSH Blobs Defined
An SHSH blob (short for Signature HaSH, blob simply referring to a blob of data) is basically a digital signature that the Apple Server uses to approve a restore process for iOS devices such as the iPad.
Why Do You Need to Save SHSH Blobs?
In order to understand why it is important to save SHSH blobs if you want to jailbreak, we are going to explain it in the context of the role it plays during a restore process.
During a restore process you open up iTunes on the computer, connect your iPad via the supplied USB cable and once the device is detected, you proceed to click on ‘Restore’. What happens then is that iTunes will send a restore request to the Apple server. The Apple server will have to respond by either rejecting or approving the request which will depend on whether the firmware that you are requesting to restore to is the current version available; ‘current’ here meaning whatever firmware versions Apple is still approving.
If the Apple server approves the request, it will send a digital signature back to iTunes which is called an SHSH blob. Only then can the restore process happen.
An ‘EXAMPLE’ Scenario: Let’s say that the latest jailbreak only works for iOS 4.3.3 and Apple has already released 4.3.4. They have also stopped signing/approving restore requests for 4.3.3. One fine day after installing some jailbreak apps on Cydia, your iPad suddenly has an error which requires you to restore the device (not common, but it can happen). Now if you have saved your SHSH blob for 4.3.3, you can use it to trick iTunes (more on how to do this in a different iML tutorial) into thinking the Apple server has signed/approved the restore request and thus be able to restore to a firmware that can be jailbroken; in this case 4.3.3. On the other hand, if you did not save your SHSH blob, you will be forced to restore to 4.3.4 which you will not be able to jailbreak. And if you are wondering why you can’t just get the SHSH blob from a website or someone else, it is because the SHSH is attached to your iPad’s ECID which makes each blob unique.
How to Save SHSH Blobs?
There are mainly 2 ways to do this:
1) ♥ Make my life easier, thanks!
*It seems that you don’t actually have to do anything now as Cydia automatically starts saving your SHSH blobs for you once you open the app for the first time. Sweet!
When you see the button that says ♥ Make my life easier, thanks! in the Cydia app’s home screen, simply tap on it and your SHSH blobs will be automatically saved on Cydia’s servers for the current iOS firmware you are on as well as all future versions. You’ll never have to remember to save your SHSH blobs ever again. However, saving SHSH blobs using this method may take up to a week depending on Cydia’s server traffic so there is a bit of a risk period.
If you want to confirm that your SHSH blobs have indeed been saved, you should be able to see SHSH: iOS (versions) in green colored text on top of ‘Welcome to Cydia’ on the Cydia app’s home screen. If it is still in the process of saving, a similar string of text should appear in red instead.
TinyUmbrella is a software you run on the computer that helps to save SHSH blobs. It is also the same software you will be using to recover and make use of the SHSH blobs when you need them. The way it differs from ‘make my life easier’ for saving is that it grabs the SHSH blob instantly rather than having to wait for Cydia to request for it (which previously mentioned may take up to a week). TinyUmbrella also saves the SHSH blobs on your computer versus on Cydia’s server as with ‘make my life easier’.
TinyUmbrella will require a bit more work but we recommend this method if you know that Apple will stop signing the current firmware that can be jailbroken anytime soon as ‘make my life easier’ has the wait period risk factor. *Apple will be releasing 4.3.4 anytime now so you will need to save 4.3.3 SHSH blobs ASAP.
We have written a step-by-step TinyUmbrella tutorial for both Windows and Mac:
- How to Save SHSH Blobs Using TinyUmbrella – [Windows]
- How to Save SHSH Blobs Using TinyUmbrella – [Mac]
Conclusion – Making Use of SHSH Blobs
We will publish a tutorial on how to use the saved SHSH blobs when the next available opportunity arises which is likely when Apple releases 4.3.4. We will link the tutorial here if you’d like to bookmark this page for easy referencing in the future.