> But I could also implement that without bringing in a block chain, right? Not only that, but they have! Signature-based authentication existed 20 years ago.

> But I could also implement that without bringing in a block chain, right? Not only that, but they have! Signature-based authentication existed 20 years ago. Register with a public key. Sign a message with your private key to authenticate. Modulo some small details to prevent things like replay, you are done. The only thing that the blockchain brings is that now lots of people have asymmetric key pairs where their public keys are published somewhere widely accessible.