In related news, graf_chokolo has now detailed how to decrypt PS3 PKGs as noted HERE.
To quote: Today he's shared his work with the public, however, it still requires some work, before it is fully functional. Right now, his code still requires the dongle master key, one that is buried within the PS3 console. The good news, is zAxis feels this key can be retrieved via a 3.15 fw console.
He is asking the community, anyone with a 3.15 console, to help retrieve this key. Once retrieved, PSGrade should become fully functional. Below, is his request to the public.