SHSH Blobs is imported for Downgrade iPhone 3G, iPhone 3Gs, iPod Touch 2G, iPod Touch 3G. SHSH blobs saved on Cydia for the firmware you downgrading on. If you don't have your SHSH files saved, you cannot downgrade iOS devices. Using Umbrella-4.01.0 for iPhone 3G, iPhone 3Gs, iPod Touch 2G, iPod Touch 3G and iPad.
Let's start Step by Step guide to help you how to saved your SHSH blobs using Firmware Umbrella.
If you want to go back to iPhone 3.1.3 / 3.1.2 or Downgrade iOS 4, iOS 4.0.1 iPhone iPod touch to 3.1.3 / 3.1.2 the following step by step guide will help you downgrade to 3.1.3 / 3.1.2 .
you have need to saved SHSH blobs, old firmwares 3.1.3 or 3.1.2.