If you don't have a situation where absolutely nobody can be trusted, then all these things become tractable with the traditional cryptography. In games you can

If you don't have a situation where absolutely nobody can be trusted, then all these things become tractable with the traditional cryptography. In games you can choose to trust a game publisher, a server, or a consensus of a few selected parties. People can prove their identity and ownership of items via a private key. A new server can accept claims signed with a public key of the previous publisher, and you could turn that into a federated system.