ECID or Exclusive Chip ID, is an unique identifier to every iDevice unit. Apple added ECID with iPhone 3GS and onward, the ECID verify and sent signatures to Apple’s servers for re-signing to get a valid SHSH. Doing this Apple has been disallowing downgrades (even via DFU Mode) on newer devices when a new firmware version is released.
ECID security is introduced to prevent us downgrading the firmware of our iDevice. When iTunes starts the process of restoring the firmware, the server asks Apple to create a sort of certificate to your device. Because the process takes place online, Apple may change the response from the server and prevent the restore to previous version. So all users who wish to preserve their jailbreak should made a backup of that file, so as to later use regardless of what Apple will invent to prevent the jailbreak.
So below are two guides to identify your Apple TV 2G ECID on Windows OS and Mac OS, after gabbing your ECID you may proceed to next procedure, where you have to save your 64KB SHSH Gold on file with Firmware Umbrella.
How Grab your ECID on Mac OS
Step 1.Put your phone in DFU Mode by following procedure How to Put Apple TV in to DFU Mode.
Step 2. Navigate to Applications> Utilities> and start “System Profiler”
Step 3.This opens a screen and you select “USB” from the block on the left.Then click on “Apple Mobile Device (Recovery Mode)” and several numbers appear low
Apple_TV_ECID
Step 4. Note the small 16 number ECID code and write down on a paper.
Step 5. To escape DFU mode restore with the firmware.
How to Grab ECID on Windows OS
Before starting download this small utility usbview Download Here:
Step 1. Put your phone in DFU Mode by following procedure How to Put Apple TV in to DFU Mode.
Step 2. Open usbview you downloaded earlier.
Step 3. In “options”, check off “config descriptors” (enable)
Step 4. Hit F5 on your keyboard to refresh
Step 5. Scroll down till you see “Apple Recovery (iBoot) USB drive, and click on it.
Step 6. Note 16 number ECID code and write down on a paper.
Step 7. To escape DFU Mode restore with the firmware.