Understanding SHSH Blobs and JB'ing for 4.2.1 HELP?

To add to this conversation: I was JB'd when I had 4.1, but then returned to 4.2.1 stock. I downloaded TinyUmbrella and it can find no saved blobs when I plug in my 4.2.1 stock iPhone4.

Shouldn't I have blobs saved from when I was JB 4.1, or would I have had to save the blobs myself manually while jailbroken? Because I definitely don't recall doing that.

 

What SHSH blobs you can saved has nothing to do with what is currently on your phone. It only has to do with what Apple is signing / sending out, right now only 4.2.1. Thus, if you use Tinyumbrella or Cydia to save your blobs, they will only be able to save 4.2.1. With Tinyumbrella, you have save them manually while Cydia will automatically save them once new ones, ie 4.3, 4.4 and so on, comes out.

 

the blobs allow you to install a specific firmware. apple only signs the blobs for the current firmware so there is no need to have the blobs backed up to install 4.2.1 right now. if you ever want to downgrade to an older firmware then you'll need the older firmware blob stored on cydia or your local computer (thru tinyumbrella or other process).

the reason that the beta redsn0w need the 4.2b3 blob is that it uses the kernel from the 4.2b3 firmware to untether. in order to use that kernel you need both the ipsw (firmware file) and the blob to allow it to be installed onto the iphone.

whether or not you'll need older blobs for the final untethered JB is unknown right now. the redsn0w in beta right now is the dev team's "backup plan". the hope is that comex will be able to untether 4.2.1 without the need for 4.2b3, but until that happens, this is what they are working on.

does that clear up OP's question?