itunes error(-1) coming when restoring iPhone 4?
Turns out, the .ipsw I was using was not the right one. I tried using iOS 5.1.1 .ipsw with stiched blobs and restored my phone, and it worked like a charm. So if anyone finds this in the future, do not try to upgrade to iOS 6.1.3 because:

1: The sHsH blobs for iOS 6.1.1, 6.1.2 and 6.1.3 are corrupted on the cydia server.
2: If you update to 6.1.3 without preserving baseband, you will lose your unlock.