Caching Apple's Signature Server
When Apple started doing this, we figured out how it worked, and the course of action was clear: to setup a man-in-the-middle attack on this server that would simply store every single SHSH that was returned for every file of every firmware version for every device owned by all of the people who cared about being able to downgrade (both jailbreakers, and App Store developers who need to test their apps on earlier firmware versions).
I built this system as a service and wrote an article about how the process worked and how it could be used. Initially, the system acted only "in the middle", but it was immediately enhanced to save all of the ECIDs of all of the users in a massive database, so it could go on its own every time Apple released a new firmware version in order to request everyone's SHSH information "en masse".
Eventually, though, you end up with so many ECIDs on file that you are trying to request from a number of servers hundreds of thousands of times fewer, that it becomes very obvious how to shut down such an operation. For a couple years now, I have thereby not been able to run the "man in the middle" proxy server, nor am I able to provide the service of automatically saving peoples' SHSH for them.
However, I have still been able to help users automatically get their data stored by having the Cydia application do it "in the field": Cydia requests SHSH blobs from Apple and uploads them to my servers whenever it notices you don't have the information stored on my servers. Additionally, I provide an API that allows third-party tools that retrieve and manage the same information to upload it to me for safe keeping.
