Comments on: Carry your PIN number in your wallet

By: Jon Wright

Jon Wright — Wed, 21 Sep 2016 07:35:49 +0000

I know this is an old topic; however I have an alternative idea to offer.
Each card usually has 16 digits + 3 more on the back.
Nearly all card issuers now allow you to select you own PIN.
Choose a set position from the card number (hint: if you put your card in most readers – not ATMs – the last 4 digits on the card are still visible) e.g. the 14th & 15th. They will almost always be different across the cards you have, add two more numbers that mean something to you (old house number, partner / parent / child birthdate / birthmonth / birthyear, part of phone number etc. etc. and avoid repeats like 00, 11… ) & there you have a 4 digit PIN that is different for each card & easy to re-generate without carrying anything else, or depending on your phone being charged!
Change you PIN at the ATM & job done!
Only thing to watch for is the bank issuing a card with a new number – then you have to change PIN again…
I find this particularly useful for cards that I use less frequently.
Major potential downside could be if you are unable to read the numbers on the card!

By: Tom H

Tom H — Fri, 04 Mar 2011 12:27:04 +0000

My pin is now in muscle memory. as proven by the fact that I can buy many drinks at a bar whilst faaaar too drunk.

By: Valerie

Valerie — Fri, 04 Mar 2011 12:25:45 +0000

Good idea, I too remember words but came unstuck when presented with a card terminal that didn’t have letters next to the numbers.

By: Dogsbody

Dogsbody — Fri, 04 Mar 2011 10:01:34 +0000

In reply to tentonipete.

No 🙂

Shapes work well too but you do need a separate shape for all your PIN’s else they will all be the same again.

By: tentonipete

tentonipete — Fri, 04 Mar 2011 09:55:51 +0000

cake = 2676?

i usually remember the shape the combination makes on the keypad

By: Dogsbody

Dogsbody — Fri, 04 Mar 2011 09:25:14 +0000

In reply to John Rutter.

Yes, a different lookup table for each card allows the pin for each card to be different but the word to be the same.

I don’t think there is any risk of using the wrong table as each table sits behind its card in the wallet but you obviously have to use different random digits for each card else it would be obvious which four letters were being used.

Humans are very bad at generating random numbers so this could be another attack vector but we are talking about very small amounts of data and a quick program or even a spreadsheet can be used to generate a more random table 🙂

By: John Rutter

John Rutter — Fri, 04 Mar 2011 08:55:20 +0000

Interesting idea. Words/letter combinations easier to remember than four digits, so see the benefit.

Do you have a different lookup table for each card?
And if so, does that pose a new risk to using the wrong table?