How Facebook Knows When Its Ads Influence Your Offline Purchases
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Re: How Facebook Knows When Its Ads Influence Your Offline Purchases
#2...aaand facebook starts to buy news pieces to justify their ad network.
this is nothing more than a press-release for their atlas feature. A new low even for wired.
Re: How Facebook Knows When Its Ads Influence Your Offline Purchases
#3>As Boland explains it, Facebook simply shows advertisers that a given number of people who saw an ad for a product also purchased that product.
Facebook doesn't share my personalized shopping data with advertisers. That's good.
But the data still exists. So the data the advertisers receive is only really anonymous until there's some sort of security breach or economic decision whereby it's suddenly more profitable to sell the personalized data. Either or Both of which are inevitable.
All in all, a moderately informative marketing piece.
Re: How Facebook Knows When Its Ads Influence Your Offline Purchases
#4tldr; it doesn't, but offline vendors that collect your contact information they can anonymously check the proportion of purchasers which might [incidentally?] have been shown their ad on Facebook's network. Only a media buyer with a budget bigger than their brain would assume causality.
Re: How Facebook Knows When Its Ads Influence Your Offline Purchases
#5tldr; it doesn't, but offline vendors that collect your contact information they can anonymously check the proportion of purchasers which might [incidentally?] have been shown their ad on Facebook's network. Only a media buyer with a budget bigger than their brain would assume causality.
Couldn't Facebook easily demonstrate causality by running an RCT? Just randomly select half of a certain demographic to show the ad to, and then show that those users are more likely to make a purchase later.
Re: How Facebook Knows When Its Ads Influence Your Offline Purchases
#6> The trick is that the hash of a phone number captured on Facebook will look just like the hash of the same phone number captured in a brick and mortar store, so the two companies can match the numbers without actually trading them.
This just isn't possible. How many cents would it cost to brute-force hash all legal American phone numbers?
Re: How Facebook Knows When Its Ads Influence Your Offline Purchases
#7> As Boland explains it, Facebook simply shows advertisers that a given number of people who saw an ad for a product also purchased that product. Facebook doesn't share my personalized shopping data with advertisers. That's good. But the data still exists. So the data the advertisers receive is only really anonymous until there's some sort of security breach or economic decision whereby it's suddenly more profitable…
Facebook doesn't share my personalized shopping data with advertisers. That's good.
The stuff about you personally that can be gleaned from market analytics will make you shit a brick.
And this is what private industry can do, not even getting into three-letter agencies.
Re: How Facebook Knows When Its Ads Influence Your Offline Purchases
#8> The trick is that the hash of a phone number captured on Facebook will look just like the hash of the same phone number captured in a brick and mortar store, so the two companies can match the numbers without actually trading them. This just isn't possible. How many cents would it cost to brute-force hash all legal American phone numbers?
Why on earth would you have to brute force all numbers? You can do this optimally: just hash the numbers you see (or get requests for).
Re: How Facebook Knows When Its Ads Influence Your Offline Purchases
#9"People voluntarily link things like phone numbers and email addresses to their Facebook accounts"
People voluntarily are idiots. Never connect a phone number to your FB account and use another mail address if you really need to have an account.
Re: How Facebook Knows When Its Ads Influence Your Offline Purchases
#10> The trick is that the hash of a phone number captured on Facebook will look just like the hash of the same phone number captured in a brick and mortar store, so the two companies can match the numbers without actually trading them. This just isn't possible. How many cents would it cost to brute-force hash all legal American phone numbers?
This is correct. As a zero-knowledge proof it is, sadly, trivially broken. (Not just in a theoretical sense. As you mention there just isn't enough entropy going into the hash. It's like asking for your age and gender, but only providing a hash to some other party so they can verify that you are who you say you are, without your divulging what information you were just given. That doesn't work - you would leak everything, because 1-100 (age) M/F (gender) only has 200 possible values. 200 hashes later your counterparty knows what you were asking to check.)
But that doesn't mean this couldn't be done properly.
There are actual zero-knowledge proofs. I liked this primer. You should read it!
http://blog.cryptographyengineering.com/2014/11/zero-knowled...
It is 100% possible for there to exist absolutely zero-knowledge proof in many instances. (Such as the one in the article.)
So, it could be possible for example (I don't know an algorithm) to check whether a phone number you were given is in someone else's set of phone numbers - without either your learning what the other's set is, or the other learning what phone number you're testing.