Hah. I don't understand. Are you suggesting I just like give people a file and tell them to email it to their stewards? How would the encryption work? I think a big part of making social backup usable is creating assurances that your stewards do in fact still have the data and can access it when needed. You need some reliable machine to machine communication for that. It doesn't have to be Nostr (in fact I am thinking about adding iroh as an alternative transport), but Nostr has the pieces I need and is also built from simple building blocks that will likely still be understandable in 50 years.