PIN: Is there a mathematician in the house?

NickX

CannyJock wrote: »

EDIT: Looks right, Nick's got the same number

Yep, my 1 in 400 figure includes the instances of all 4 digits being the same.

As you exclude these, we are exluding 10 combinations, so I think this reduces the figure to 1 in 390.

Been a long time since I did theory or probability though


EDIT : My mistake here, I agree with ChattyChappy that the figure is reduced to 1 in 360.

NickX

chattychappy wrote: »

For 3 digits the same (and 4th one different), the maths is more complicated:

Number of digits that could make up the repeated digit = 10
Number of digits that could make up the "other" digit = 9
Number of positions the "other" digit could appear in = 4

Therefore the number of combinations with 3 digits the same = 10 x 9 x 4 = 360.

You are right here, my mistake, if we exlude the instances of all 4 digits being the same, it is 1 in 360.

Getting complicated now

cse

Hardly in the mathematical spirit of the thread I know, but most cards will block PINs that are 4 numbers the same, 4 consecutive numbers, or 0852/2580 (straight up/down the middle of the keypad) as "unsafe" PINs - too easy for a fraudster to guess I suppose. This means that you will not be issued any of these numbers randomly, and you won't be able to change your PIN to any of these

James

IMHO if you're never going to use your credit card to make a cash withdrawal why use a PIN?

In the event of your credit card being used fraudulently with your PIN, prior to you reporting it lost or stolen, then the first thing you'll be asked is - "How did the crook get hold of your PIN?" Why put yourself in that position?

An safer alternative is to get hold of a CHIP & SIGNAURE CARD - You never have to worry about keeping your PIN secret. Best of all is no cardholder liability.

chattychappy

James wrote: »

An safer alternative is to get hold of a CHIP & SIGNAURE CARD

Unless you happen to be my mate who had a knife held to this throat by some bloke demanding his card(s) and the PINs. Two blokes - one was to wait with my mate whilst the other used the cards.

Cost with PIN: £700
Cost without PIN: ????

OK... a bit of an extreme point, but I do now fear taking cards out for which I don't know the PIN.

never-in-doubt

James wrote: »

IMHO if you're never going to use your credit card to make a cash withdrawal why use a PIN?.

You need a PIN to spend anything on the card - not cash!

James

never-in-doubt wrote: »

You need a PIN to spend anything on the card - not cash!

Sorry if the Credit Card is Chip & Signature - you'll never need to worry about at PIN, keeping it secret, or your card issuer, ATM's, and Chip & PIN machines having the ability to keep it secret.

never-in-doubt

James wrote: »

Sorry if the Credit Card is Chip & Signature - you'll never need to worry about at PIN, keeping it secret, or your card issuer, ATM's, and Chip & PIN machines having the ability to keep it secret.

Ahh ok lol, thanks for clearing up. Ok, so who issues these 'Chip & Signature' cards cos my bank don't and i've never been given the choice...

roofusb

I have Chip & Sig cards with Egg and Virgin. Although they don't advertise the fact, Chip & Sig cards are available from all issuers - you just have to ask (repeatedly in many cases!).

Virgin were a bit harder to convince - they said they only offered them for people with a disability who found it difficult to use PINs. So I wrote to them saying I 'had a problem' with using Chip & PIN (the problem I have is due to the transfer of liability from the card issuer to the consumer, rather than any disability, but I didn't mention that :-)), and they must have assumed I was disabled - got a new (pink!) Chip & Sig card a week or so later.

Egg issued one without any problems upon request.

bert&ernie

The PIN is simply one method of cardholder verification in the EVM chip card standard. All issuers are obliged to offer EMV cards set to request a signature rather than a PIN. This is ultimately down to disability discrimination. However you will have to request it - they wont offer it. Disability legislation also means they cant actually ask you about the disability. Suffice to say, if you want a Chip and Signature card, they have no grounds to refuse the request.

Beware that some Chip & Sig cards will not work in unattended terminals like garage forecourts, and you obviously wont be able to use an ATM to obtain cash.

I like to think they are a must have accessory for those who like to sport a tin foil hat and prefer a belt with their braces.