Dev team earlier advised iPhone users not to upgrade to iPhone OS 3.1 beta firmware but must save their iBEC and iBSS Signature Certificates of iPhone OS 3.0 for upcoming Jailbreak tools. Despite warnings, most of the users have updated their iPhone to OS 3.1 beta firmware (intentionally or accidentally) and now finding way to downgrade back to iPhone OS 3.0 firmware. Follow our simple guide to Downgrade iPhone 3GS 3.1 to 3.0 OS Firmware. During Restore or Downgrade of iPhone & iPod Touch users may encounter certain iTunes errors and 16xx errors.
iH8sn0w has just released iREB tool for Windows and Mac that can troubleshoot errors like “16xx” and “21” from iTunes that are displayed after a restore or an iPhone OS firmware downgrade in iPhone 2G, iPhone 3G and iPod touch 1G. Johnny Franks is in the process developing the Mac version of iREB 3.1-3 for iPod Touch 3G. iREB utility is based on iDevice and dfu-util that uploads 3 pwned files, so that iTunes can accept custom IPSW firmware/downgrade to lower firmwares.
Note - iREB does NOT jailbreak, it just disables iTunes’s ability to upload a patch to the ramdisk to block custom firmware made by PwnageTool.
Download – iREB for Windows XP/Vista/7
Download – iREB for Mac OS X 10.4/10.5/10.6