How to downgrade 4.3.2 to older firmware ,iphone ios downgrade

If you have upgraded to iOS 4.3.2 using the latest ipsw update files or through iTunes , you can downgrade back to older firmware 4.3.1 if you have saved shsh blobs for that firmware on Cydia . Read How to use TinyUmbrella to save SHSH Blobs. The shsh blobs are required for the downgrade , without which the process cannot be completed .
#Tip: Bookmark this page as a handy tutorial for future reference . Press Cltr+D and save the bookmark in your browser .
Follow the step below to downgrade 4.3.2 to older firmware :

1. Download older ipsw files 4.3.1 4.2.1
2. Put your device in DFU Mode . [Quick Tip : How to put your device in DFU Mode]
3. Download TinyUmbrella used in later steps to bring your device out of Recovery Mode .
4. Launch Notepad in Administrator Mode
5. Open the following file location using Notepad C: /Windows /System32/drivers/etc/ and locate “hosts” file .
6. Replace the last line of the file with the following address 74.208.105.171 gs.apple.com
7. Launch iTunes and connect your device . iTunes will ask to restore your phone . Press and hold Shift key on your keyboard and click on Restore on iTunes .
8. Select the downloaded ipsw file in Step 1 and proceed with the restore [downgrade]
9. Dont forget to remove and replace 74.208.105.171 gs.apple.com from hosts file after the process is complete .

Use TinyUmbrella to bring your device out of recovery . Click Exit Recovery .
If you get error 1600 or error 3194 , use iReb to put your device in DFU mode and try again.