Restoring custom IPSW made with PwnageTool or Sn0wbreeze without pwning the iBoot in your iDevice results in Error 1600. If you will try to restore using recovery mode, iTunes will throw Error 21 and if you will try to restore custom IPSW using normal DFU mode, you will get Error 1600. To fix this error, you must put your iDevice into Pwned DFU Mode using iREB.
Fix iTunes Error 1600 on Windows:
- Download iREB for Windows from here
- Connect your iDevice to your PC via USB cable.
- Close iTunes window if already opened.
- Launch iREB and click on the name of your iDevice.
- Now use the following instructions to put your iDevice into DFU mode:
- Hold down the Home+Power button simultaneously for 10 seconds.
- After 10 seconds, release the Power button but keep holding the Home button until iREB detects your iDevice in DFU mode.
- As soon as iREB will detect your iDevice in DFU mode, it will patch the iBoot using Limera1n exploit.
Fix iTunes Error 1600 on Mac:
Unfortunately, iREB is not available for Mac users but there is a workaround to avoid 1600 iTunes error on Mac using Redsn0w. Just follow step-by-step guide here to put your iDevice into Pwned DFU Mode using Redsn0w 0.9.7b6.