Its going to be on top of nostr and not just for identity. The idea was to not have a centralized server at all and I had two options for that. Either use Arbitrum and write a smart contract or I could covert these notes into data points on nostr and use that. I do the calculations on the client side yes, because its just some additions and subtractions. The only important thing is to store the data somewhere where people can sync together and use their own thing if they want to. And yes you are imagining the correct thing! I am also naive with the ways of nostr so its a good learning experience