[How To] Save SHSH Blobs for iOS 4 Firmware

Notcom recently released TinyUmbrella 4 (a unified version of Firmware Umbrella and TinyTSS) to save SHSH blobs of the iOS 4 firmware.

Firmware Umbrella:

When you try to restore any of the devices listed below to an older firmware, you will quickly come to realize that Apple doesn't allow you to do that. Once you have upgraded, downgrading is usually not an option Apple condones. The way they stop you from doing that is basically by a simple response that iTunes receives when you try to restore to the firmware of your choosing. The firmware for the devices is signed with a unique id (known as 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 the valuable information and sends it to your device. Your device then checks the information and verifies the signature (making sure it came from Apple, as it can't be forged since the encryption is very high). Once the signature matches then the restore process can continue. If it doesn't match, the device raises an error in the restore process and stops. Apple also started the trend of ceasing to sign older firmwares once a new one is out. Firmware Umbrella sends the same exact request that iTunes sends Apple when requesting the signatures for the device to be restored. It saves SHSH signatures that your device receives from the Apple server and allows you to downgrade the OS indefinitely.

TinyTSS:

TinyTSS is a small java app that basically acts as your very own signature service. The app checks if you are allowed to restore to the version you are requesting when iTunes verifies the firmware restore for the devices mentioned below. With TinyTSS alongside with the SHSH blob file(s) obtained from Firmware Umbrella, you will be able to restore to the version of those SHSH files forever.

TinyUmbrella:

Tiny Umbrella is Firmware Umbrella + TinyTSS combined.

TinyUmbrella Supports:

• iPhone 3GS
• iPod Touch 3G
• iPod Touch 2G (with model number MC)

Note:

• TinyUmbrella can now save iOS 4 SHSH regardless of whether your iDevice is jailbroken.
• You can save SHSH blobs for iOS 4 even if you’re on OS 3.1.3 or older.
• iPhone 3G and older devices including iPod Touch (Non-MC) users do not need to save any SHSH blobs.
• Tested on iTunes 9 and all versions after (up to and including 9.2)

Download TinyUmbrella:

• Windows
• Mac
• Linux