

Your shopping habits are uniquely identifiable - somberi
http://www.theverge.com/2015/1/29/7945073/credit-card-metadata-reveals-purchase-history-study

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kshatrea
Patterns are uniquely generated in almost all types of information. What has
been missing until the great rise of the World Wide Web is intent to monetize.
Earlier companies sold you products like Microsoft Windows, Coca-Cola and
Apple Macintoshes. Advertising paradigms like television advertising, radio,
newspapers while really nice, had a "last-mile-connectivity" problem - you
never really knew how you got your customer - through TV, radio? I do
understand Nielsen and other ratings companies and some TV analytics
historically try to ameliorate this, but the internet has been the greatest
driving force in the last few years. Google and Facebook etc. and internet
driven content engines have all traded eyeballs for content or products. As a
result, the intent to improve advertising for the eyeballs (since presumably
the eyeball count has a theoretical upper bound) has become the force du jour.
Hence the ability to identify stuff was there, except for the machine learning
part which has grown up from academia tremendously. It is just that now we
have the intent to use all this to identify and collect patterns from all
sorts of data. Whether that is good or bad or gray is another matter.

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junto
My role in the house is to buy the cat food and the hard liquor.

I imagine someone at the supermarket statistics centre studying my shopping
habits and wondering how one family can survive on whisky and Friskies Chicken
& tuna dinners.

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mattzito
It's not that uncommon - I had a meeting with wal-mart's data team once where
they talked about how there are certain pairs of purchases that are highly
correlated with male shoppers - beer and diapers was one I remembered.

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greggyb
I came in expecting something like an Amazon shopping history. I don't find it
too surprising that in-person purchases can be tracked so readily - geographic
information is a huge dimension to add to these data. It would be interesting
to see how many data points are necessary to achieve similar accuracy just
with a purchase history. Particularly interesting would be matching users
across websites.

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bruceb
While obvious to say, use cash.

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Jekyll
May not be long before shops go cashless. With increasing numbers of people
using the magic plastic - cash may fade out over time. Also, bank notes (at
least in the UK) sometimes have serial numbers so it isn't wholly foolproof.

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code_duck
In the US, banks and most businesses who accept cash track the serial numbers
of 50 and 100 denominated bills. I would imagine that banks keep a handle on
the serials of their 20s as well, which are by far the bills most commonly
dispensed from ATMs.

~~~
hga
"[citation needed]"

Most banks don't include the 2 I use, one of which is not small, nor does the
grocery store that's the target of many of those $100 bills.

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code_duck
My work experience includes working in retail where we hand recorded the
numbers on large bills each night and in the morning. I'm pretty sure banks
track these numbers; what makes you believe yours don't?

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hga
But that's _completely_ useless for this purpose unless the bank supplying the
cash also recorded the numbers, and "mostly harmless" even if they were (see
below).

What makes me sure the banks I use don't suitably track the numbers is that I
show up to them with $20s just acquired from an ATM (saves time) and they
don't take any actions that would allow recording of the numbers of the $100s
they give me in return. The bills just come out of a slot in the usual drawer,
the teller only count them by hand to make sure they're all $100s and that
she's giving me the right number of them. I'd add that _many_ people would
notice if she ran them through an OCR machine before handing them over....

What you're talking about sounds more anti-counterfeiting efforts, $100s
having of course the highest payoff, and at worst case they only reveal that
person X shopped at that establishment the day before. Which I suspect is not
typically damning, e.g. that I shopped at a grocery store without any details
as to what I bought suggests that I'm a human that eats food, little more.

I wouldn't say I'm "paranoid" about this sort of thing, i.e. I pay cash
locally more to avoid credit card fraud than to keep details about myself
private, but I read the appropriate SF when I was young, and being a hacker in
the sense of this forum I pay _close_ attention to these things. As of yet in
my corner of SW Missouri there's no sign of them.

~~~
code_duck
The last time I with Drew a large sum from the bank, he did run it through
accounting machine and most of those have OCR abilities.

Businesses I've been involved with write down the serial numbers of high
denomination bills when cash drawers are filled. I wouldn't be surprised if
banks were aware of which serials were in their cash drawers for inventory
purposes basically.

It's true that the only real tracking that goes on with serial numbers
currently to catch criminals is recorded cereals in bank robberies and black
market transactions. However, the capability is there to construct some small
amount of conclusions about regular people based on where bills go. I wasn't
saying it's widely in use for everyday surveillance.

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stygiansonic
Direct link to the research paper: ("Unique in the shopping mall: On the
reidentifiability of credit card metadata")

[http://www.sciencemag.org/content/347/6221/536.full](http://www.sciencemag.org/content/347/6221/536.full)

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joshfraser
You can also buy anyone's entire credit card purchase history directly from
FirstData (the behind the scenes processor for most of the credit cards in the
world). It's not cheap, but it's most definitely for sale.

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amelius
What these tools do is "generalize", which is essentially the same as
"discriminate".

(If someone makes generalizing assumptions about another person, then whether
this is based on shopping-behavior, or skin-color, is not relevant.)

Hence such tools should be forbidden, or at least their use restricted.

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jerf
We should be so lucky. The problem with these tools is _precisely_ that they
successfully specialize, in substantial and generally-reliably detail.

~~~
amelius
No, the problem is that if these tools are incorrect then they are falsely
discriminating. If they are correct, then they are freaky. And then there is
the problem that you don't know _when_ they are correct.

There's just too many things fundamentally wrong with this kind of application
of technology.

