To me the problem should be modelled similar to what we have now: Some institutions (private or public) giving an ok or not ok on the keys. And platforms choosi

To me the problem should be modelled similar to what we have now: Some institutions (private or public) giving an ok or not ok on the keys. And platforms choosing which institutions to trust. At some point we may have platform choosing all governments+trustworthy institutions You could make things like a "smart contract" returns your money (or triggers an investigation) if after 48 hours you report an issue with your account or transaction. Of course this would mean some change on the blockchains themselves