Charlie Cabot, Research Lead, Privitar, re-identifies a location trace live on the In:Confidence 2019 main stage (April 4th at Printworks, London).

1. Privitar.com
Let’s re-identify
a location trace

2. Cell towers
The British Library
Green Park South Bank
Sir John Soane’s Museum
Printworks
1/1/19 10:35am
1/1/19 10:07am
1/1/19 11:12am
1/1/19 10:44am
1/1/19 2:01pm
St. Paul’s Cathedral
1/1/19 12:01pm
What is a location trace?

3. Source: mastdata.com
• In the Canada Water area, where we are
now, there is a ‘tower’ every few blocks
• In urban areas ‘towers’ are often small
structures on top of buildings, not tall
freestanding towers
Every few blocks
• Towers are pinged when you move to
a new cell, send or receive a call/text,
or start a data session
Every few minutes
How detailed are location traces?

4. Background information about location traces
is available online
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5. We have
some background
information about
someone in the
audience
Is it enough to
identify them?
PLEASE STAND UP

6. They were in Southwark at 11pm on Wednesday
If you were in the borough of
Southwark at 11pm Wednesday,
stay standing!
Otherwise, or if you’re not sure,
sit down!

7. They were in Westminster at 9am on Monday
If you were in the city of
Westminster at 9am Monday,
stay standing!
Otherwise, or if you’re not sure,
sit down!

8. They were in Greenwich at 9pm on Saturday
If you were in the borough of
Greenwich at 9pm Saturday,
stay standing!
Otherwise, or if you’re not sure,
sit down!

9. They were in Newham at 7pm on Saturday
If you were in the borough of
Newham at 7pm Saturday,
stay standing!
Otherwise, or if you’re not sure,
sit down!

10. They were in Hackney at 2pm last Thursday
If you were in the borough of
Hackney at 2pm last Thursday,
stay standing!
Otherwise, or if you’re not sure,
sit down!

11. They were in Newport at noon on Monday
If you were in the Newport,
Wales at noon on Monday,
stay standing!
Otherwise, or if you’re not sure,
sit down!

12. Re-identified!

13. Takeaways
1. It only takes a few data points to single out an
individual
2. Re-identification leads to privacy harm
• Stalking
• Disclosure of hospital visits
• Disclosure of who you’re meeting up with
3. Generalising locations to borough level didn’t work
4. For more, see papers on unicity by Yves-Alexandre
de Montjoye
Thank you for participating!
Source: De Montjoye, Yves-Alexandre, et al. "Unique in the crowd: The privacy bounds of human mobility." Scientific reports 3 (2013): 1376.