The Living Thing / Notebooks :

Differential privacy

Another thing I won't have time to blog or fully understand, but will collect a few explanatory blog posts about for emergency cribbing.

Learning Statistics with Privacy, aided by the Flip of a Coin:

Let’s say you wanted to count how many of your online friends were dogs,
while respecting the maxim that, on the Internet,
nobody should know you’re a dog.
To do this, you could ask each friend to answer the question
“Are you a dog?” in the following way.
Each friend should flip a coin in secret,
and answer the question truthfully if the coin came up heads;
but, if the coin came up tails, that friend should always say “Yes”
regardless.
Then you could get a good estimate of the true count from the
greater-than-half fraction of your friends that answered “Yes”.
However, you still wouldn’t know which of your friends was a dog:
each answer “Yes” would most likely be due to that friend’s coin flip coming
up tails.

Refs