If that seems like a lot of trouble over a numeric keypad, you haven't cracked open an ATM lately. The modern "PIN entry device" is a physically and logically self contained tamper-resistant unit that encrypts a PIN within milliseconds of its entry, and within centimeters of the customer's fingertips. The plaintext PIN never leaves the unit, never travels over the bank network, isn't even available to the ATM's processor: malicious code running on a fully compromised Windows-based ATM machine might be able to access the cash dispenser and spit out twenties, but in theory it couldn't obtain a customer's unencrypted ATM code.
I assumed that ATM keypads were just plugged into the PS/2 port. Apparently not!
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