I think I've meet something like this before, but it was in a distant memory. You're not... happen to be the same team who propose to sell this "selective" data, right?
The data dialogue takes place between the 2 counterparties, the user (or data subject) and the organization (the data controller). They hold the public and private keys therefore we have no access to the keys and the data is effectively useless to any third party, including ourselves. We don't want to add to the big problem which exists, so we built the whole system to privacy by design principles with input from Dr. Ann Cavoukian.