Downgrade iOS 6.1.3/6.1.4 impossible now as Apple shuts signing window
 

It was already known that Apple would shut the signing window once it released iOS 7. Those looking to downgrade iOS 6.1.3/6.1.4 are now out of luck as these firmwares are no longer being signed. Anyone who either wanted to downgrade from iOS 7.0 to the aforementioned versions or from iOS 6.1.4 to iOS 6.1.3 [...]

http://vr-zone.com/articles/downgrad...signing-window