To the Math wiz out there, the ideal solution would be an SP address that can be derived from the pubkey directly in such a way that nobody needs to "set it up" with a supporting client.

The goal is to send money to any npub without having to rely on whatever they are using as a client.

Of course, that would only make sense if the same derivation blocks the public from combining all silent payments to an npub into a single balance.

Zap events then would have to contain a proof of a bitcoin transaction without identifying it directly. Otherwise, anyone would simply merge all Zap Events to find somebody's balance on chain.

Let's hope somebody can find a solution here.