diff -r f65e4fa6e902 -r 38ef1ef6082d handouts/ho07.tex
--- a/handouts/ho07.tex	Wed Jun 01 13:04:21 2016 +0100
+++ b/handouts/ho07.tex	Tue Jun 14 11:41:16 2016 +0100
@@ -46,6 +46,39 @@
 %% cupit re-identification attack
 %% https://nakedsecurity.sophos.com/2016/05/20/published-personal-data-on-70000-okcupid-users-taken-down-after-dmca-order/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+nakedsecurity+%28Naked+Security+-+Sophos%29
 
+%Differential privacy
+%=====================
+%https://www.wired.com/2016/06/apples-differential-privacy-collecting-data/
+
+%Differential privacy, translated from Apple-speak, is the
+%statistical science of trying to learn as much as possible
+%about a group while learning as little as possible about any
+%individual in it.
+
+%As Roth notes when he refers to a “mathematical proof,”
+%differential privacy doesn’t merely try to obfuscate or
+%“anonymize” users’ data. That anonymization approach, he
+%argues, tends to fail. In 2007, for instance, Netflix released
+%a large collection of its viewers’ film ratings as part of a
+%competition to optimize its recommendations, removing people’s
+%names and other identifying details and publishing only their
+%Netflix ratings. But researchers soon cross-referenced the
+%Netflix data with public review data on IMDB to match up
+%similar patterns of recommendations between the sites and add
+%names back into Netflix’s supposedly anonymous database.
+
+%As an example of that last method, Microsoft’s Dwork points to
+%the technique in which a survey asks if the respondent has
+%ever, say, broken a law. But first, the survey asks them to
+%flip a coin. If the result is tails, they should answer
+%honestly. If the result is heads, they’re instructed to flip
+%the coin again and then answer “yes” for heads or “no” for
+%tails. The resulting random noise can be subtracted from the
+%results with a bit of algebra, and every respondent is
+%protected from punishment if they admitted to lawbreaking.
+
+%https://www.cis.upenn.edu/~aaroth/Papers/privacybook.pdf
+
 \section*{Handout 7 (Privacy)}
 
 The first motor car was invented around 1886. For ten years,