PSA: Jailbreak for iOS 6.1 imminent! Get those SHSH Blobs saved NOW even if you do not plan to Jailbreak!
It makes me sad when I can't help someone jailbreak their iOS device because they do not have their SHSH blobs properly saved and accessible. I've written this post to hopefully educate some of the newbie Jailbreakers out there, as well as light a fire under some folks who may be procrastinating on this (as I have done in previous versions of iOS).
Even if you are not planning to Jailbreak your iOS device or not planning to right away it is crucial that you save your iOS 6.1 SHSH blob ASAP.
Because it is highly likely that shortly following the release of the jailbreak, Apple will release iOS 6.1.1 that fixes the exploit and then stops signing iOS 6.1.
What does Apple not signing iOS 6.1 mean?
It means that unless you save your SHSH blob, your hardware will be "locked" out of ever downgrading back to iOS 6.1.
Can I just stick with iOS 6.1 and not update if Apple patches the jailbreak exploit?
Yes! However, if ever anything at all goes wrong (which is common when tinkering with deep hacks) and you need to restore your device you can forget about re-jailbreaking because iTunes will restore to the latest version of iOS that Apple is signing. You need to have your iOS 6.1 SHSH blob for your device handy in order to restore iOS 6.1 onto your device once Apple stops signing.
What the hell is an SHSH blob?
How do I save my SHSH blob?
The best way I know of is to use Tiny Umbrella. Tiny Umbrella will save your SHSH blob files on your local storage. For more information see: http://thefirmwareumbrella.blogspot.com
If you do jailbreak, then Saurik's Cydia store *may* save your SHSH blob for you automatically. There is a prompt when you first install Cydia that asks you if you want his server to save your SHSH blobs. It should be noted that there have been periods of time where Saurik's server was not properly saving SHSH blobs. He assumes no responsibility (of course) and offers the service as a mere convenience. If you are serious about Jailbreaking at all, I would recommend familiarizing yourself with Tiny Umbrella.
Anything else I need to know?
The rumors I've read in various spots on the Interwebs indicate that an OTA vs a full restore generate two different SHSH blobs for a device. I take this to mean if you have saved your SHSH blob associated with your OTA update, then that will not be good enough. You will need to do a "fresh" iOS 6.1 install. That is basically what I am doing now, as I type this up :).
I have a few years of experience Jailbreaking various iOS devices. I'm certainly no skilled iOS developer or hacker. Just a humble user. If you have any specific questions regarding jailbreaking and SHSH blobs I may be able to help. There are already other threads that cover what to install and tinker with once your device has been jailbroken, so please use those threads for what they are and keep to the subject of SHSH blobs in this thread.