Messages are signed nostr events. Use the key you seal gold with in Tideholm (stored in this browser only, never sent anywhere), or a NIP-07 extension if you have one.
Or paste a 64-hex nostr private key:
A signed kind-0 event: this is how the room, the nostr.social directory and every nostr client name you. Existing fields are loaded first, so editing never wipes a profile.