how to generate "SIG check key" for v2 prx ?

on psp FW 2.xx
each psp have different "SIG check key" prx file

how to gen. this key for v2 prx ?




ata.prx software dump from FW2.01 EBOOT.PBP







ata.prx hardware dump from PSP(2.01) NAND Flash







ata.prx hardware dump from PSP(1.51 -> 2.01) NAND Flash




this "key" was gen. by psp when update

so is there have method to gen. this "key"?