Difficult question. If an AI will successfully pass a Turing test, then this AI can trick the whole PKI mechanism (even if quantum computers exist). The only thing when the AI will fail the mandatory appearence personally - "in the flesh".
But the KYC will not be enough, this is not a question.
On the other hand there will be some specialized AI system that could filter the " tricky" AI.
And there will be AI that tricks the filtering AI and so on.