I tend to think bank cards should have two numbers.
The one you see on the face of the cards would be used for online transactions and would have a delayed funds availability policy.
The second one would be on the chip and would settle with a far faster funds availability policy, normally instantaneous.
Or a two-factor authentication where you reply to a message to your phone to approve a transaction. Something you know - Your credit card number, Something you have - your cell phone. You could also approve on your cell phone with a PIN to add another “something you know” factor.