HD keychains do this with a whole keychain. you can just do the same thing. seed key, path /identify /encrypt. then you can chain those as well. you can do xpubs. we haven't even touched what we could do with this. nostr identities become hd keychains with different derivation paths for different roles. revocability is not given in this but rotation can be done every time by marking the message with a tag. so even if one message is revealed, it is tagged, and only that tag is breached.

i think this is called forward secrecy. anyway. *yawn*