TinyUmbrella allows you to take backups of SHSH blobs (ECID SHSH). Hackers have previously figured out a way to use the SHSH blobs to downgrade to older iOS versions even after Apple stopped signing the firmware file.
Even though it is not possible to downgrade to iOS 6.x.x with the SHSH blobs currently due to the changes incorporated by Apple in iOS 6, it is still a good practise for jailbreakers to take a backup of the SHSH blobs.
Semaphore, developer of TinyUmbrella writes on his blog:
TinyUmbrella has been updated to work with iOS 6.1.2 on relevant devices. Make sure you don’t update to 6.1.3 when it drops. I wasn’t able to get 6.1.3 beta included (I just got too busy). But if you desire to keep your jailbreak, avoid 6.1.3 like the plague.
It is also may be a good time to update to iOS 6.1.2 as evasi0n jailbreak won’t work with upcoming iOS 6.1.3 software update. But please note that you will be able to take a back up of the SHSH blobs for iOS 6.1.2 even if you’re on older iOS version.
If you’ve jailbroken your iOS device using evasi0n then Cydia would have already saved the SHSH blob for iOS 6.1.2 on its servers. TinyUmbrella allows you to save the SHSH blobs locally.
As always, let us know how it goes.