SHSH Blobs – Everything You Need to Know
Before explaining you how to use the SHSH blobs you first need to know what they are and why they are so important for you. SHSH blob is a small piece of data from the Apple’s digital signature protocol. This protocol is responsible for iOS restorations and updates and it can also control which iOS version an iDevice can support. Apple, whenever you update your iOS version, updates the SHSH blob to allow only the newest iOS versions to be installed to your iDevice, but the hackers community found a way to modify it and let you install any iOS version you want to your iDevice.
SHSH Blobs – Some Technical details
SHSH blobs is not Apple’s official term, the original term is System Software Personalization. The SHSH blobs are created by a hash formula which includes the iDevice’s type, the signed iOS version and the ECID identification number of this device (it is a unique number on the device’s hardware). The way that Apple restricts a user to restore an iDevice to a specific iOS version, is that Apple refuses to generate this hash during the restoring procedure. The outcome of this refusal, is that an Error Code will appear to your screen during the Restoring process.
Why SHSH Blobs are important?
First you need to know that if you have not saved the SHSH blobs from a jailbreakable iOS version, there is not a way to downgrade to that iOS version. In order to be able to you effectively the SHSH blobs, is to always save them whenever you are on a jailbreakable iOS version and whenever you are upgrading to a new iOS version. You can only downgrade your iDevice to an iOS version that you have save the SHSH blobs.
Apple managed to add further security to their newest iDevices and to the ones that support iOS 6.x.x. If you have already upgraded your iPhone 3GS/3/4S to iOS 6.x.x there is no way to downgrade it to 5.x.x iOS version, even if you have saved the SHSH blobs from that iOS version.
You can read the following articles about the SHSH blobs: