November 12th, 2010, 1:31 pm
If "brute force" means punching the card holder in the mouth a few times, then not long. If all four digits can take on any of 10 values (0-9) and pins are random, then it takes an average of 10000/2 tries.If all four digits can take on any of 10 values (0-9) and pins are human-created, then it takes less time if I have access to a database of human-created pin numbers (such a database might reveal that "1234" is an extremely common pin number).If I don't have to enter all 4 digits -- unentered digits resolve as leading or trailing zeros (e.g. "1 ENTER" == "1000 ENTER") then 999+99+9 of my tries will require fewer button presses.