The general theory of operation for building a custom IPSW is:
Because of these protections, custom IPSW files can generally only be restored under specific conditions: modify ipsw file
This is one of the most critical and often-overlooked steps. The BuildManifest.plist contains checksum values for each file in the IPSW. If you modify any file, you must update its corresponding checksum in the manifest. Otherwise, the verification process will fail. The general theory of operation for building a
iBoot64Patcher iBEC.raw iBEC.patched --sig-check-off Otherwise, the verification process will fail
An open-source reimplementation of Apple's restore process. It can restore firmware to iOS devices using either a compressed IPSW file or a directory containing extracted IPSW contents.
Apple only "signs" the latest iOS version for any given device, meaning you cannot officially install older versions. However, by modifying an IPSW and using bootrom exploits like checkm8, advanced users can downgrade 64-bit devices to previous iOS versions. Tools like powdersn0w enable this for certain legacy devices running iOS 5 or iOS 7.