Why do ATMs accept any PIN? states that the ATM does not know my pin and the pin is not on the card as well.
My bank has this system:
It works in 5 stages:
- I enter my debit card number on the website;
- The website gives me an 8 digit code to enter on the machine;
- I insert my card into the machine, press the M1 button and enter the 8 digit code;
- After the code is entered, the machine asks me for my 4 digit pin and and immediately says if it's correct (by stating "PIN OK");
- The machine then gives me a 7 digit code to enter on the website, which authenticates me.
How can this machine know that my code is valid if the code is not on my card? Note that the M1 and M2 buttons are not memory buttons, but instead buttons that start a certain workflow: M1 is for authentication with the system and M2 is for digitally signing my transactions.