Is there a way to prove the origin of an npub on #Nostr? #AskNostr

My initial thought would be to hash all the list of all npubs on a relay at a given time and post it on the #timechain using opentimestamps.org nostr:note18xsafz3ajp6wqx5zyhflf7x3va55uzlnt76pqe8mdn9s6l9g00msjz0jv8