A few days back we showed you how to save iOS 11.1.2 blobs, so you could downgrade back to iOS 11.1.2 even if Apple stops signing the firmware file. It can be quite handy with the possible release of iOS 11.1.2 jailbreak.
However, if you’re on iOS 11.2 and have saved the SHSH blobs then you may still run into an issue, as the iOS 11.2 SEP (secure enclave processor) firmware is not compatible with iOS 11.1.2 or lower firmware. reddit user minh6a explains:
So it came to my realization that people are pretty complacent with saving blobs for 11.1.2 and lower without checking compatibility of SEP.
11.2 baseband is 8.30.01, while ALL LOWER iOS 11 firmware use 8.01.00. Thus, as we already know, when SEP/baseband are different, high chance it is incompatible with the firmware.
He used the iOS 11 ipsw firmware file and iOS 11.2 SEP firmware to restore iPhone 6s using futurerestore. While he was able to restore to iOS 11, Touch ID didn’t work. When he restored to iOS 11 with the iOS 11.2 SEP firmware, Touch ID worked fine. I didn’t quite get the relationship between SEP firmware and baseband.
If you’re on iOS 11.2, then you will be able to restore to any iOS 11 version but you will still hit an issue with Touch ID because of the incompatibility of the iOS 11.2 SEP firmware. So it is recommended that you downgrade to iOS 11.1.2 before Apple stops signing iOS 11.1.2 firmware. If you need help, then check our step-by-step guide on how to downgrade to iOS 11.1.2 without losing data.
It is widely expected that Apple will stop signing iOS 11.1.2 firmware this week or could even be as early as today, so don’t miss this opportunity to downgrade to iOS 11.1.2 so you can jailbreak your iPhone, iPad or iPod touch when the iOS 11.1.2 jailbreak is released.
Apple has stopped signing iOS 11.1.2 and iOS 11.1.1 firmware files. So you can no longer downgrade your iPhone, iPad or iPod touch to iOS 11.1.2.