This work analyzes one of the most common PIN algorithms, VISA PVV, used by many ATM cards (credit and debit cards) and tries to find out how resistant is to PIN guessing attacks. By "guessing" I do not mean choosing a random PIN and trying it in an ATM. It is well known that generally we are given three consecutive trials to enter the right PIN, if we fail ATM keeps the card. As VISA PIN is four digit long its easy to deduce that the chance for a random PIN guessing is 3/10000 = 0.0003, it seems low enough to be safe; it means you need to loose your card more than three thousand times (or loosing more than three thousand cards at the same time :) until there is a reasonable chance of loosing money.
