nostr:npub12h88wrwwh99mjfzm8x9gx7989a07mqw7tynvvacx888eus4fh44q33mz5h nostr:npub1j5l9mm3k5rwafe8c89x5uyfrlly26nkkv69frje6jjf85yaeqcwqfvwxv4 it provides a standard way for a web browser to do an interactive back and forth to sign a challenge as a way to offload user agent ACL to the server side.