Let's say ...

an authority has collected all privatekeys, e-mail account accesses, passwords ...
and gave it to a person who is now claiming that he is Satoshi.

This 'Satoshi' can ...

sign a message, make transactions from Satoshi's accounts, send Satoshi e-mails, claim that he is Satoshi.

But he is not the real Satoshi.

How?

Maybe we will find the real Satoshi but we will never know that he is the real Satoshi as nobody can prove it. He can prove that he is the owner of all privatekeys, passwords, accesses but the owner of these can be anyone.

Yes, you got it.

It is impossible to prove that somebody is Satoshi.


Even if Satoshi presents his privatekeys, signs messages, shows his passwords, e-mail account accesses... it could be someone else who has all these privatekeys, passwords, accesses now.
He would only prove the ownership of these but it is impossible for somebody to prove that he is Satoshi.

Even if Satoshi presents his privatekeys, signs messages, shows his passwords, e-mail account accesses... it could be someone else who has all these privatekeys, passwords, accesses now.
He would only prove the ownership of these but it is impossible for somebody to prove that he is Satoshi.