If you dont have your key , read the drive first , save the key. Now in source you will have your dumped firmware it will ask to autoload. "Select no" manually load the ofw for your drive and hit spoof to target. Keys should now match . Vendor and write. Take update then flash lt+1.9 . All done .
Side note....... Ofw for all drives is in the 1.9 folder if you no longer have yours. Also if you do you can simply load it in source instead of reading the drive again.