Credit card x,y, and z all know my current balance, place of residence and payment history. They let me and only me know that info via some method that can be trusted by anyone (blockchain?).

At a later date, I autorize credit card w to access some computed score that I compute and verify via other trusted means (another blockchain or whatever). Credit card w never sees all my data and the verifier gets access to only what it needs. Nobody needs to trust anyone and instead trusts the chain. Just an idea.