I wrote this as a starting point, no thanks to nostr:npub1aljazgxlpnpfp7n5sunlk3dvfp72456x6nezjw4sd850q879rxqsthg9jp 's idea:

The Higher relay specializes in providing a Nostr relay with access to keys derived from a master key. Any keys which are not derived from the master key will be rejected for write events.

https://github.com/bitkarrot/higher