Just a heads up for all the new iPhone 4 and 3GS owners. you need to save your iOS4 SHSH Blobs (ECID SHSH) . This will allow you to restore back to iOS4 if for some reason you which to downgrade your firmware because of a new release from Apple. If you don’t save your SHSH Blobs they you will not be able to downgrade. This is usually done when you open up Cydia as Saurik has been saving this information for everyone on the 3.x.x firmware. However I don’t know if this is occurring for iOS4.

Here is more information on how Tiny Umbrella works, this is directly from their website thefirmwareumbrella.blogspot.com

If you have one of the following devices:

• iPhone 3GS
• iPod Touch 3rd Generation (32 or 64)
• iPod Touch 2nd Generation (with a model number MC)

Then you have probably noticed that Apple does not let you go back down to older firmware versions for your device. Once you ‘upgrade’ they don’t let you downgrade. The way they stop you is basically by a simple response that iTunes receives when you try to restore the firmware of your choosing. See, the firmware is now signed for the above devices. It is signed with a unique id (ECID) that only your device has. Apple takes the firmware version files and combines them with your ECID and generates a hash that ONLY APPLE can generate. iTunes packages up this valuable information and sends it to your device. Your device checks the information and verifies the signature (making sure it really came from Apple because it CANNOT be forged as the encryption is very high). If the signature matches then the restore process can continue. If the signature does not match, the device raises an error and the restore process stops. Thanks to Saurik (Jay Freeman) we all now know how to circumvent this. Apple only provides this signature for firmware versions while the firmware version is ‘Active’. So once a new firmware version is out, Apple stops signing the older version and only signs the new version. This is why you cannot get 3.1.2 signatures anymore. Apple is currently only signing 3.1.3 signatures (and 3.2 for iPads). This will change when the next firmware is released. Soon 3.1.3 (and 3.2) firmware signatures will be a thing of the past and Apple will only sign the next one. The version is important. If you do not have the EXACT signatures for the exact device (ECID) for the exact firmware version, you cannot restore that device to that version. PERIOD. So, if there was a way to save that signature for later use, we could bypass the need for asking Apple (only to have them say ‘No’) to restore our firmware. If you have a jailbroken device, you can visit cydia and your shsh will be saved ‘on-file’. But if you are not jailbroken yet, or if a jailbreak has not yet been released for the firmware your device is on, you are just out of luck as you can only get cydia if you are jailbroken. This is where TinyUmbrella comes in.

I’ve compiled the following Guide on how to store your SHSH Blobs using TinyUmbrella.

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Step 1: Download TinyUmbrella from thefirmwareumbrella.blogspot.com for your OS (Windows/Mac)

Step 2: If you’re using a Mac, double click on “Umbrella-4.00.26.dmg” and drag the Application within the .dmg file to your desktop. Otherwise you will have issues. For Windows just run the file from where ever you have downloaded it to.

Step 3: Run TinyUmbrella and plug in your Device (3GS/iPad/iPhone4/iPod Touch). It will then display your Firmware currently on the Device, as well as the device Model/Baseband and other informaiton.

 

Step 4: Click “Save My SHSH”, and the program will save your SHSH for your device base on whichever Firmware is currently being singed by Apple. And in this case its 4.0, which you can see below in the screenshot. The Firmware 3.x.x is no longer being signed.

 

You should now be able to restore your iPhone at anytime to 4.0 using the SHSH you’ve just generated using the same tool. Just click Start TSS Server, make sure its running like in the Screenshot shown below.

 

Then you just need to Open iTunes 9.2 and do a restore making sure you hold down “Alt + Shift” for Windows and “Option” for Mac when clicking restore. Then you should be able to restore your iPhone to whatever Firmware you’ve generated and saved SHSH keys for.

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