Today iPhone hacker iH8Sn0w released an update to iFaith shsh blob dumping software. Now it supports IOS 6+ A4 devices including iPhone 3GS/4 iPod touch 4 running IOS 6.It only supports Windows.
STEPS OF SAVING SHSH:-
Step 1) - The first thing you will need to do is download iFaith v1.5.3 from here
Step 2) - Once you download iFaith v1.5.3you will need to extract it to your Desktop (or whichever location you downloaded iFaith v1.5.3
Step 3) - Next you will need to launch iFaith v1.5.3 by double clicking on the iFaith-v1.5.3.exe file.
Step 4) - With iFaith v1.5.3up and running you will simply need to click the Dump SHSH blobs button.
Step 5) - Read the instructions/information on the next window and then click the Proceed button followed by the Let’s Go! button.
Step 6) - You will now be at a screen where you must put your iPhone, iPod Touch or iPad into DFU mode. Follow the on-screen instructions
Step 7) - Once your iPhone, iPod Touch or iPad is in DFU mode iFaith 1.5.3will begin grabbing your SHSH blobs.
Step 8 ) - When the SHSH blob grabbing process is complete you will need to select a SAFE directory to store your SHSH blob cache.
For DFU mode tutorial click here