Location Obscuring

draft-thomson-geopriv-location-obscuringGEOPRIV, IETF-79Martin Thomson

Goals

• Pick an obscuring distance.• Take a series of known locations, which might

have greater accuracy than the recipient is permitted to receive.

• The obscuring process produces a series of reported locations.

Static Case

Constant Updates

When to Update

When to Update: Whoops

Hidden Trigger

Varying Hidden Trigger

Problem

Very Small Uncertainty

Recast Problem

Continuous Random Field

Interpolation

A B

C D

But the Earth isn’t flat

Skewed Interpolation

A B

C D

grid / cos(latitude)

grid / cos(latitude)

Uniform Distributed Interpolationt=0.5

t=0.3

t=0.2

t=0.1

r = a(1-t) + bt

a b

P(r)

Goal: Uniform distribution of offset

Interpolation

Demonstration…http://held-location.sourceforge.net/js_geoshape/maptest.html

Alternative