> People would submit their national ID number or full name, and get back a crypto key, and there could only be one key per national ID?
Usually, with a KYC service, people submit photos of their identity documents, and sometimes also video of themselves vouching for the document (as if you were having an asynchronous conversation with a notary public.)
Later, if someone else comes along and tries to register the same credentials and also presents the same level of evidence, you get a human arbitrator involved and ask each party to present more evidence, e.g. another primary identity document, or an actually-notarized letter of identity claim, etc. The same sort of things you give the police in an identity-theft case.
https://telegram.org/blog/passport, for example.
> People would submit their national ID number or full name, and get back a crypto key, and there could only be one key per national ID?
Usually, with a KYC service, people submit photos of their identity documents, and sometimes also video of themselves vouching for the document (as if you were having an asynchronous conversation with a notary public.)
Later, if someone else comes along and tries to register the same credentials and also presents the same level of evidence, you get a human arbitrator involved and ask each party to present more evidence, e.g. another primary identity document, or an actually-notarized letter of identity claim, etc. The same sort of things you give the police in an identity-theft case.