SHSH blobs or ECID SHSH is a unique digital signature that Apple assigns to each iPhone, iPod Touch and iPad.

Whenever you connect your iPhone 3GS or iPod Touch 2G/3G or iPad to iTunes to restore or update iPhone OS firmware, the ECID is sent to Apple servers for authentication and iTunes will proceed to restore the device only if the ECID authentication is complete. 

However, when a user installs the new iPhone OS firmware, the digital signature associated with the earlier firmware is erased. This makes it difficult to restore the iDevice to its earlier firmware. 

Saurik, the creator of Cydia has setup a server, which basically mimics Apple’s verification server so that you can downgrade or restore back to the older firmware by making use of the SHSH blobs.

If you have jailbroken your iPhone 3GS, iPod Touch 2G/3G or iPad then this is important because you might want to restore your iPhone to an older firmware if the newer version includes patches that plug the loopholes used to jailbreak the iPhone OS. As you might know, it took the iPhone hacking community, more than two months to release the software tools to jailbreak iPhone OS 3.1.3. So MuscleNerd of the iPhone Dev Team has strongly recommended users to take a backup SHSH blob to future proof it for jailbreaking. 

This tutorial will take you through the step by step instructions to backup your ECID SHSH or SHSH blobs of your iPhone 3GS, iPod Touch 2G/3G and iPad. This tutorial is only for iPhone 3GS, iPod Touch 2G/3G or iPad users who own a Mac. If you are a Windows user, you can checkout our step-by-step guide for Windows users.

Step 1: Click here to download the latest version of the Firmware Umbrella application to your Mac.

Step 2: Double click on the downloaded zip file to extract the file.

Step 3: On your Mac, navigate to Applications -> Utilities -> Terminal to launch the Terminal window.

Step 4: In the command prompt, enter the following text and hit Enter :

sudo /Applications/TextEdit.app/Contents/MacOS/TextEdit /etc/hosts

Step 5: You may be prompted for a password. Enter your administrative password. This will launch the TextEdit application.

Step 6: Look out for a line that contains gs.apple.com. If you find one, remove it and save the file

Step 7:  Double click on the Firmware Umbrella folder on the desktop and launch the Umbrella.dmg file. From the mounted file, click and drag the Umbrella application to your Mac desktop

Step 8: Double click and launch the Umbrella application from your Mac desktop.

Step 9 : You will now be prompted to input your ECID, device version and to select a SHSH repository

a. If you do not know your device ECID, put your iPhone into recovery mode. From the Apple menu, select 'About This Mac' -> More Info -> USB (Hardware menu). On the right side pane, select 'Apple Mobile Device (Recovery Mode)'and copy your ECID from the 'Serial Number' field.

b. In the SHSH repository, select 'Saurik-Cydia' from the dropdown menu. This will check Cydia for SHSH and in case it doesn't exist, it will be stored there. Alternately, you may also select 'Apple' to query Apple for your SHSH.

Step 10 : Click on 'Submit' button. Once Firmware Umbrella has completed processing the data, you will be displayed a 'SHSH Saved!' message as seen below.

Step 11 : A .shsh file is now created in the Firmware Umbrella folder on the desktop. Save this file for future use.

The process to backup your SHSH blob on your Mac computer is complete. We hope you found this useful. Let us know how it goes in the comments. 

[via iClarified]