Signed IPSW files can be restored via iTunes. Unsigned IPSWs cannot currently be restored via iTunes.
✓ | iPod touch 4 | iOS 6.1.6 (10B500) | 21st February 2014 | 889 MB | iPod4,1_6.1.6_10B500_Restore.ipsw |
✓ | iPhone 3G[S] | iOS 6.1.6 (10B500) | 21st February 2014 | 823 MB | iPhone2,1_6.1.6_10B500_Restore.ipsw |