It's 100% work. Read & use these lines
1.Download the iOS 6.1.2 ipsw file & ifaith v 1.5.3 & redsn0w v 0.9.15b3
2. Now open ifaith v1.5.3 & select your shsh blobs & create a new 6.1.2 ipsw file.
3. Again open ifaith & use the ireb , your phone has gone in DFU MODE.
4. Then open iTunes & restore your iPhone with new 6.1.2 ipsw file created with ifaith.
After complete the iTunes process your iPhone display completely black.
5. LAST STEP: Now open the REDSN0W v0.9.15b3 select EXTRA , then EVEN MORE & click on RESTORE button , then select iOS 6.1.2 simple (without created by ifaith or non- Faith file.)
REDSN0W show a unexpected error
BUT IGNORE IT.
Some process has work on your Iphone then complete the process. YOUR IPHONE HAS START AS A NEW IPHONE ON IOS 6.1.2 .