I stopped to get gas after work. I swiped my debit card and the pump asked me for my zip code.
Being a curmudgeon and assuming the gas pump was hassling me for marketing data, I lied to the gas pump. 55555 I entered. The gas pump told me to see the assistant inside.
Access denied, turkey.
Turns out the gas pump wanted the zip code to compare it against the billing address of the card. Pretty smart. That’s basic two-factor authentication – authenticating your identity by providing two factors – something you have (a debit card) and something you know (the billing zip of the debit card). Progress.