Cydia saves your iPhones’ SHSH blobs to their servers when the app is installed on a jailbroken iPhone, the SHSH blob file is a security hash file that allows your iPhone to install a particular version of Apple’s iOS software, you can see which ones are saved for your device by checking out the top of the screen when you launch the Cydia app on the iPhone.
What SHSH blobs are on Cydia
You can verify a SHSH blob that is stored locally with redsn0w (how you get them locally – check Tiny Umbrella), you navigate to where the file is stored and let redsn0w verify it.
You can also query Cydia servers to verify what remote blobs are stored for your device
You can pretty much do the whole gamut with blobs in redsn0w:
Send blobs on your device to Cydia by using the ‘Fetch‘ button, normally this shouldn’t be necessary but if you can’t see the iOS version in your Cydia app at the top of the screen then it may help. You can do the same thing manually with an actual blob file by using the ‘Submit‘ button.
Stitching Blobs to a IPSW
You can also in redsnow take your SHSH blobs either from a local directory or remotely from Cydia server and ‘stitch’ them into a IPSW firmware file. Get to this by clicking the ‘Stitch‘ button, then selecting the IPSW then choosing the SHSH blob – this way you can restore to a IPSW firmware – well I find it hard to see why you would bother doing this anymore as redsn0w now can do this on the fly with restores in the latest versions. But hell you can do it if you want!
Using Tiny Umbrella
To get these SHSH blobs to your local computer a handy application called Tiny Umbrella will be your friend.
– Launch Tiny Umbrella, Ok the dialog on requesting SHSH from Cydia
– Connect the iPhone and highlight it in the connected devices
– Click save SHSH
– A list of your saved SHSH blobs are displayed
– To see the directory where they are saved or set a new one, do these things in the Advanced Tab, by default on OS X these are saved in an invisible directory in the home account named “.shsh”, for easier access create a new folder without a period and then select it by clicking on the ellipse ‘…’ and setting that folder – then click ‘Save SHSH’ again and Tiny Umbrella will fetch and store the SHSH blobs to the new location.