Are you any good at remembering numbers? Most people I've met say they're not.
What would you say if I told you that I have a way of remembering all the PINs on all of my credit and debit cards - a way that doesn't require me to remember ANY numbers at all? Would that be of any interest to you?
Different 4-digit numbers for each card that can't be forgotten and don't need to be written down anywhere.
Derive the PIN from the account number that's already printed on the card.
That account number is an ISO 7812 number ('ISO' = 'International Standards Organisation'). These numbers can have a maximum of 19 digits, but almost every credit and debit card I've seen has 16 digits, in four groups of four, embossed right there on the card. It looks like this:
0123 4567 8912 3456
Four groups of four? I need 4 digits for a PIN...
... so what's stopping me picking the first four (0123) and using those as my PIN for this card? Those four are as good as any other four I might pick at random - unless of course lots of people already use those four (which according to that ISO standard I mentioned above will be common to a great many cards) and if the credit card thieves know that lots of people use these four then -- maybe it's not such a good idea to use those four after all.
So what about the second four? Well, I could use those (4567). Or the third four (8912). Or (you guessed it) the fourth four (3456). Simple.
But we're on a roll - let's not stop here. What about picking the first number from each group? (0483). Or the second number from each group (1594), third (2615)... or the fourth from each group, but this time: backwards! (6273).
Last from group 4, first from group 1, last from group 3, first from group 2 (6024).
Third from group 3, first from group 2, second and third from group 4 (1445).
____ 2___ __1_ _34_ = ____
0123 4567 8912 3456 = 1445
OK, I quite like that last, I'll go with that. I've got two other cards, let's see what their numbers are if using the pattern '____ 2___ __1_ _34_' :
____ 2___ __1_ _34_ = ____
9876 5432 1098 7654 = 9565
1111 2222 3333 4444 = 3244
9565 and 3244.
Best of all, I don't have to remember any numbers to recall the PINs. All I have to do is visualise where those numbers are in the pattern, and bingo :)
I can now:
- go to any hole-in-the-wall cash machine, or any shop with chip-and-PIN
- pick any card
- look at it
- see the PIN
- hand the card over
- enter the PIN
- get the card back
- forget the PIN.
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© Colin Reynolds / Typocheck 2007