When Apple launches a new version of iOS, it soon stops signing the previous version, making it totally impossible to go back, either for reasons of performance or stability or for wanting to do Jailbreak instead of waiting indefinitely to be Make compatible with the new version.
Once Apple stops signing its iOS versions it becomes impossible to install an older version of the operating system, even from iTunes. This is because there is no master key that enables or disables these versions, but the signature is based on the unique Electronic Chip ID (ECID) of each device.
Apple uses SHSH2 Blobs to sign iOS versions with each user's ECID so that a downloaded iOS version can only be installed on a particular device. Luckily, while Apple continues to sign up for an iOS version, it is possible to get the SHSH2 Blobs so that, even if you stop signing it later, with this file and a tool called Prometheus we can downgrade our iPhone or iPad.
Next, let's look at how to get these SHSH2 Blobs easily using a simple Telegram bot. Before proceeding, we must copy the ECID needed to generate this file. To do this, we can use the UDID Calculator application, available in Cydia, or connect our device to the computer and, from iTunes, click on "Serial Number" until we see the ECID.
Get and save the SHSH2 Blobs to be able to downgrade iOS in the future
The first thing we have to do is download and install Telegram on our iPhone or iPad and log in with our phone number.
Once done, access the following link to connect to the bot and start talking to him by sending a "/ start" command. Next, we send a command "/ shsh" to indicate that we want to generate the Blobs and will ask us for the information corresponding to our device.
We select our device and then ask us for the version of iOS for which we want to download the SHSH2 Blobs. We can only download it for the versions that are still being signed by Apple, so, for example, we will not be able to download it for iOS 9.3 or for other versions that the bot tells us.
In the next step, we will ask for the ECID of our device.
We paste it into the text box and send it to the bot. This will automatically connect to the Apple servers, capture the SHSH2 and save it to a file. After a few seconds, we will be able to download this file.
Once downloaded we must save it well because, if we lose it, we will lose any possibility of a downgrade in the future after Apple stops signing the previous version of iOS.
How to verify that the SHSH2 Blob iOS file is correct
In addition to the checks that appear in the previous capture, to check if this file is correct and will not give us problems when signing the versions of iOS when we want to do Downgrade to an iPhone or iPad, all we have to do is access the Next page , upload our Blob, select the device we use and the version of iOS for which it has been generated.