Around 2016, with the release of iOS 10 and the iPhone 7, Apple realized the blob loophole was still too wide. They introduced two massive roadblocks: SEP and APTicket.
For the technically inclined, SHSH blobs are deeply rooted in cryptography. The system relies on a challenge-response authentication. shsh blobs
Without a valid blob, your phone will reject the iOS version, even if it is an official Apple file. Around 2016, with the release of iOS 10
The SEP manages your passcode, Touch ID, and Face ID. When you restore iOS, the main OS and the SEP firmware must be compatible. Critically, Apple signs SEP firmware separately from the iOS system. Without a valid blob, your phone will reject
If you try to downgrade to iOS 14 using blobs, but the latest signed SEP is from iOS 17, the restore will fail. Your iPhone will bootloop because the old OS cannot talk to the new, incompatible security chip.
