SHSH blobs made by Apple and this consist of Hash signature System. They restrict downgrade iOS in the Apple devices. Apple has done everything to stop jailbreaking their devices. SHSH blobs mainly involve with the downgrade iOS.
Click Redsn0w extras than you can see following window
Redsnow is great jailbreaking tool and it has an ability to verify SHSH blobs in your iDevices. You can fetch, verify or use SHSH bobs with Redsnow.
Verify – If you already have blobs then those files can be verify using this step. You can select bobs from your computer to verify.
Submit – In this step you need to select bobs and submit files in to the Cydia server. (You’r computer must content correct blobs).
Query – You can find ECID in your device and enter from here. It will send this query to Cydia server for available blobs for device.
Stitch – This option you can personalize IPSW with your blobs. You can select IPSW file using this and also by clicking you can select SHSH blob file. This Youtube video clearly explain this.
Follow this Youtube video that will be useful to you.