That link was very useful. The riff structure is very similar although the signature algorithm is different.
I have some bad news. The IDPS has been confirmed as the plain IDPS with no variations (I expected it to be user ID). That means that some step is missing in the paid algorithm. For some time, people have been able to use DLC bought by other people by changing their user ID. That means that info could be extracted on any PS3, so a value coded by IDPS (which is different on EACH console) can not be part of the algorithm. I think that the value calculated by 471 is some kind of signature to validate act.dat. It will fail on different console which explains why the act.dat is deleted every time the machine boots.
So I'm going to restudy the VSH looking for the missing part. We don't know the meaning of byte 0x810 to 0x1010 of act.dat. Previously I discarded that the act.dat contained an entry for each content as it has a fixed size but it is the only place to store keys. It is a slow process so please be patient.
Meanwhile we can improved make_self_npdrm and decrypt updates (for disc games).
By the way more info on keys:
VHS CURVE TABLE:
I apologize for providing an incomplete solutions and I hope that me or someone else completes the info.