Preventing Baseband Update

Edit options.plist

1. Unpack Custom IPSW
2. Decrypt Restore Ramdisk using xpwntool and mount it
3. Navigate to /usr/local/share/restore
4. Edit options.plist on the restore ramdisk

(Ignore the SystemPartitionSize in your plist file and leave it)

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>UpdateBaseband</key>
        <false/>
</dict>
</plist>

5. Reencrypt the restore ramdisk
6. Repack the IPSW
7. Prepare device for custom firmware using redsn0w Just enter pwned DFU option
8. Restore IPSW to iTunes in pwned DFU Mode

This method works on iOS 4.2.1

This won't work with original IPSW. Pwned DFU mode doesn't patch sigchecks in iBSS, so the ramdisk won't load. You need to load patched iBSS/iBEC for this to work.

baseband SHSH block

because of thte iPhone 4 needing baseband SHSH to update the baseband porting the host file to saurik's server or running TinyUmbrella will allow this request for SHSH to be ignored

1. port the host file to Saurik's Server server or run TinyUmbrella
2. update to 4.2.1

this will not work on pwnd firmware

swap ramdisk

open the ipsw in a zip editor and replace the ramdisk names with each other then follow the Edit options.plist guide above.