thats the idea. sha2(privkey + “topic”)
Nice. Probably can do some other cool things with EC maths. For example I could generate a secret and send you somethings (coins, RGB toke, UDA etc.) and you would not know. But when I reveal the secret to you, you can see it in your wallet, though I cant take it back.
@bumi added master keys to alby too, so we should have a look at how they do it