You can't use SHSH blobs to go to i OS 8.1.2, but it's still being signed, which means you can just restore to a downloaded IPSW.There is an easier way to do what you want, though, and you won't even have to re-jailbreak.Step Two Right click or control click the Red Sn0w application that you extracted in Step One and click Run as Administrator from the popup menu that appears. Step Seven You will be asked if you would like to Prevent baseband update. Step Eight You will be told that Pwned DFU mode is required. Step Nine Connect your i Phone to the computer, turn it off, and click Next Step Ten Red Sn0w will now guide you through the steps to get into DFU mode. Hold down both the Home button and the Power button for 10 seconds.
After a few seconds, it shows "Connect to i Tunes".
When i Tunes reminds you to enter the recovery mode, press "Shift" on the keyboard and click "Recover".
Then connect your i Phone to the computer with USB cable.
Step 2: After the software recognizes your device, choose Recover from i OS Device on the Fone Lab interface and click Start Scan.
As we all know, the normal restore procedures for i Phone will download the latest software to your device automatically through i Tunes.