A hacker under the nickname Tihmstar, as promised, has released a solution to downgrade the iOS version no longer signed by Apple. A free utility called Prometheus.
The program allows you to switch to iOS version (downgrade or upgrade) that stopped signing Apple. The main condition for a successful transition – the presence of a previously saved certificate SHSH blobs. The developer has released a detailed video tutorial on working with Prometheus.
To use Prometheus you must have a certificate in a special format shsh2. They need to be preserved in a time when Apple still signs the iOS version data. This can be done using TSSchecker using the manual from this link.
If you have a saved certificate, everyone will be able to downgrade to an earlier iOS version. We are talking about the possibility to downgrade / upgrade the version of iOS 9.x and iOS 9.x. The transition is possible between iOS 10.x and iOS 10.x. It is also possible to upgrade with iOS 9.x iOS 10.x, but downgrade from iOS 10.x on iOS 9.x can be done.
If the user has no saved SHSH blobs, it will update your device to new iOS, then not being able to roll back the firmware, it will lose the jailbreak. In order to avoid this, you need to save a digital signature.
Prometheus only supports 64 bit devices and is available in a version for macOS. Versions for Windows and Linux in development. To learn about how to use prilozheniem at the video:
If your device is not jailbroken and you want to downgrade with blobs SHSH2, for you manual below:
Download the first version of Prometheus available for free at this link.