How to store private information on a Hook?

I'm still new to Hooks and C in general but how can a Hooks developer store personal and confidential information on a Hook (e.x: Full Name, Age, ID) without it being publicly available.

I'm planning to code a Hook that only accepts KYC/AML enabled accounts' transactions to avoid unwanted transactions to the receiving account.

Any centralized or decentralized structures are accepted. Thank you.