[Cryptography] De-Anonymizing

[Christian Huitema]

> I generally pay with cash at the local supermarket.  But I have one of 
> those store tracking things that a mate gave to me.  So his purchasing 
> pattern is intermingled with mine.  Which is probably not a lot of 
> confusion, can be stripped out if it is known.

That reminds me of a story from the 70's, when "electronic pass" where
starting to be introduced in enterprises. One particular insurance company
embraced it with gusto, requiring a badge read when crossing lots of doors
inside the building. Every week, the manager would get a detailed report of
where the employees had been, which corridor they crossed, even how much
time they spent in the restrooms. Unusual patterns would result in an
extended "one on one" between manager and employee.

Needless to say, said employees were not happy. So, they devised a simple
counter-measure. At the beginning of the week, they would drop all their
electronic badge in a basket, and then pick one at random.

-- Christian Huitema