OP why don't you just decrypt the firmware? Download the
firmware to your Desktop and change the extension to ZIP and extract it. Then download
VFDecrypt and unzip it to your Desktop. Once you've extracted the iPhone firmware files, locate the 018-7063-114.dmg and drag it to the Desktop. Now open up Terminal and type in, without quotes, "cd ~/Desktop" enter "./vfdecrypt -i 018-7063-114.dmg -o decrypted_fs.dmg -k 2ab6aea67470994ec3453791ac75f6497c081edd1991e560a61dd666ac4b73f43c781739". When done you should have the decrypted iPhone 4 4.1 filesystem in a dmg labeled decrypted_fs on your Desktop. At this point you can delete the other files you downloaded.