1aqp·hace 3 años·discussSorry, I wrote that comment too quickly. It is close to impossible to recover ka, kb and ka.kb.P, even given A=ka.P, B=kb.P and P.
1aqp·hace 3 años·discussAn important point to note, that is not very obvious from the text, is that it is (very, very) difficult to retrieve ka from A=ka.P and kb from B=kb.P. For an attacker who has A and B, it's close to impossible to recover P and ka.kb.P