Apple released a detailed paper on its use of Local Differential Privacy, and the big takeaway everyone has grabbed hold of is which emoji is most popular. Oh, and it’s the Face with Tears of Joy. There, you’re welcome.
Super Cool Math Stuffs
Really, I shouldn’t blame a bunch of my peers for focusing on the fun piece of information in this story. Apple’s three page paper is filled with all kinds of smarty-pants brainiac stuff like this:
The noise injection step works as follows: After encoding the input as a vector using a hash function, each coordinate of the vector is then flipped (written as an incorrect value) with a probability of 1/(1 + 𝑒𝜀/2), where 𝜀 is the privacy parameter. This assures that analysis of the collected data cannot distinguish actual values from flipped values, helping to assure the privacy of the shared information.
I have no idea what that means. And really, the hearty-eyes emoji is way cooler and it’s the fourth most popular emoji.
Data Collection Techniques
Now, if you are someone for whom the above quote means something, Apple details two techniques it uses to collect data while protecting our privacy: The Count Mean Sketch and the Hadamard Count Mean Sketch. Both techniques insert random information into data being collected. That random information serves to effectively obfuscate any identifying aspects of that information so that it can’t be traced back to individuals.
- Participation in data collection is voluntary, and users have to opt-in when setting up or upgrading a device.
- Apple limits who within the company can see even the privatized data.
- Apple’s system drops IP addresses from the information gathered.
- Data is kept for a maximum of three months.
- The company also limits the number of “contributions” any one person makes based on the type of data being collected. All types are limited to one or two contributions per day.
All of which means that most users can feel comfortable about Apple collecting data from their devices—data that is used to make iOS, macOS, tvOS, watchOS, and Siri smarter—without feeling like their lives are being pillaged for profit.
Which Emoji Is Most Popular?
But who cares?! Amiright? What’s really important is that skull/death emoji that is, for some reason, the 7th most popular emoji for Apple customers.