We need to make sharded nsecs the default for Nostr.

Amethyst partially signs with its share of the nsec and sends to Amber. Amber can only finish the signature or reject. Amber should not be able to reassemble the nsec from any event from Amethyst (or any other app).

Now repeat this for every single Nostr app.

No single app has the full nsec. The only way to "leak" an nsec is to break into the code of both apps at the same time.

Frost does that. But for singing only.

We also need sharded encryption and decryption schemes.