iFaith aka ProjectiF is the first public SHSH dumper
As we speak, @ih8sn0w is demonstrating and explaining his latest project, ProjectiF, which has been revealed to be named iFaith. iFaith is the first program of it's kind. It is an SHSH dumper which can dump a firmware blob(needed to downgrade firmware) from your currently installed firmware, even if Apple is no longer signing that firmware and you didn't save your SHSH while it was being signed.
Download iFaith 1.0 here
Basically, when your device comes from Apple, it comes with a firmware pre-installed. If Apple is no longer signing that firmware, you wouldn't be able to save the SHSH blobs in the past. With ih8sn0ws new tool, you can dump the SHSH blob directly from your currently installed firmware. The way this works is that Apple has signed image files that show up during the boot sequence with the SHSH blob. iFaith allows you to dump your SHSH key directly from those files.
After you have dumped the files, you then patch the firmware file you are trying to downgrade to with your SHSH key, this firmware file is considered a signed firmware file. Once you have created it, you simply restore it in Pwned-DFU mode just like you would if you were restoring any other custom firmware. iFaith is compatible with mostly all iDevices except for the iPad2 and a few others.
Below ih8sn0w explains the program in further detail:
description="iFaith SHSH Dumper Preview"