iPhone 4 GSM 3,1 upgrade I'm using iOS 5.1.1 (9B206). I want to upgrade my iPhone to iOS 6.1.3, but I don't know how to do this. I have tried downloading the IPSW of iOS 6.1.3 to upgrade, but it doesn't make any changes. The second time, I try building file SHSH with IPSW, but that didn't work either. Any ideas for this problem to upgrade from 5.1.1 (9B206) to ios 6.1.3 ?
Unfortunately you can't upgrade to another version other than the latest iOS version, as your iPhone requires to have the software verified with the apple servers to sign it.

There use to be a fix to this by blocking the connection of iTunes with Apple server or diverting it to a custom server but this can't be done anymore.

So your best bet is to continue using iOS 5.1.1 or upgrade to 7.1.1