Weirdest credit card coincidence ever? OR...

December 8, 2016 3:14 PM

I just got a new Visa and a new Discover card each with new numbers but they have the same 3 digit security code. Is that just a massively wild coincidence?

My purse was stolen on Monday and in it were 2 credit cards. I just got them both replaced. One Visa (Capital One) and one Discover. New numbers. Same expiration date as the old ones. BUT the freaky thing is that they have identical 3 digit security codes.

Are these security codes tied to something about me? Or is this just the happiest of coincidences? At least now, I stand a very good chance of always remembering the code correctly.

posted by susandennis to Work & Money (9 answers total)

Best answer: The 'security code' is the output of your credit card number being encrypted by the bank when the generate the card. It's just an additional secret piece of information, but not particularly different in class or security than your normal number. It's pretty unlikely that you'd get 2 of the same numbers, but certainly not impossible (there's only 1000 options for a 3 digit one afterall) and not at all worrying in any way.
posted by so fucking future at 3:23 PM on December 8, 2016 [13 favorites]

I was recently helping my mother in law order something online and noticed that her 3 digit security code was the same as mine. Different credit card companies but both Visa. Very mysterious!
posted by platinum at 3:30 PM on December 8, 2016

There are over 500k credit cards in the US with that exact same security code. You getting 2 at the same time is rare but not super freaky rare. There's a small number possible codes and a lot of cards (around half a billion based on stats I've seen)
posted by missmagenta at 3:35 PM on December 8, 2016 [3 favorites]

Best answer: Two of my cards have had the same code, too.
posted by blackzinfandel at 3:41 PM on December 8, 2016

It isn't that weird. There are probably around 100 million Americans with two or more credit/debit cards. That means that there are more than 100,000 people in the US with two matching card security codes in their wallets.
posted by rockindata at 3:50 PM on December 8, 2016 [3 favorites]

Best answer: If you're curious how they're generated.

Just coincidence, by the laws of probability it's going to happen to a bunch of people, you happen to be one.
posted by Candleman at 3:56 PM on December 8, 2016 [1 favorite]

Response by poster: Fascinating!! Ask MetaFilter for the win... again!

Thanks all!
posted by susandennis at 4:19 PM on December 8, 2016 [1 favorite]

Those codes are effectively random numbers. The probability that you get two cards that happen to have the same number is 1 in 1000. (I think? If I'm wrong someone will correct me).
posted by Nelson at 5:02 PM on December 8, 2016 [1 favorite]

Because of the birthday paradox, the probability of 2 cards having the same code goes up rapidly the more cards you have.
posted by w0mbat at 5:29 PM on December 8, 2016 [4 favorites]