W3C home > Mailing lists > Public > public-geolocation@w3.org > March 2010

RE: Location fuzzing

From: Thomson, Martin <Martin.Thomson@andrew.com>
Date: Thu, 25 Mar 2010 02:21:54 +0800
To: John Morris <jmorris@cdt.org>, Doug Turner <dougt@dougt.org>, public-geolocation <public-geolocation@w3.org>
Message-ID: <8B0A9FCBB9832F43971E38010638454F03E24ED197@SISPE7MB1.commscope.com>
Ahh, John beat me too it, I see :)

> -----Original Message-----
> From: public-geolocation-request@w3.org [mailto:public-geolocation-
> request@w3.org] On Behalf Of John Morris
> Sent: Wednesday, 24 March 2010 10:36 AM
> To: Doug Turner; public-geolocation
> Subject: Re: Location fuzzing
> 
> Doug, some methods were previously discussed on the list (see below).
> I'll check on the current status of these approaches....  John
> 
> On Nov 8, 2009, at 5:52 PM, Thomson, Martin wrote:
> 
> > There is an alternative method in:
> >
> > http://tools.ietf.org/html/draft-thomson-geopriv-uncertainty-

> 03#section-4.4
> >
> > This discusses a method that could be used to prevent some of the
> > basic attacks on a “fuzzed” location.  It’s basically the same
> > algorithm, but it prevents accidental reveals of location through
> > multiple requests by maintaining a fixed offset at any one
> > location.  There’s a method described for hiding the fixed offset.
> >
> > From: public-geolocation-request@w3.org [mailto:public-geolocation-
> request@w3.org
> > ] On Behalf Of Richard Barnes
> > Sent: Sunday, 8 November 2009 9:37 PM
> > To: public-geolocation@w3.org
> > Cc: Doug Turner
> > Subject: Location fuzzing
> >
> > Hey all,
> >
> > I got a question from Doug a little while ago about location
> > fuzzing, and thought the whole group might be interested in the
> > response.
> >
> > The current approach we're taking in GEOPRIV is described in this
> > document:
> > <http://tools.ietf.org/html/draft-ietf-geopriv-policy-21>
> > Geodetic fuzzing is in Section 6.5.2 ...
> > <http://tools.ietf.org/html/draft-ietf-geopriv-

> > policy-21#section-6.5.2>
> > ... and fuzzing of civic addresses is in Section 6.5.1:
> > <http://tools.ietf.org/html/draft-ietf-geopriv-

> > policy-21#section-6.5.1>
> >
> > These techniques start from a slightly different place than the W3C
> > Geolocation API:
> > -- Geodetic location is given by a shape (e.g., point, circle,
> > ellipse, polygon, arc-band), rather than a single point with a radius
> > -- Civic location is given by an RFC 5139 address structure
> >
> > The geodetic fuzzing algorithm take two inputs:
> > 1. A shape representing the user's estimated location, and
> > 2. A "fuzzing radius" F in meters
> > From these, you generate the fuzzed result in the following way:
> > First, you choose a random "baseline circle" that  (1) has a radius
> > at least F, and (2) covers the input shape (the user's location).
> > The shape you return is then any shape that contains the baseline
> > circle.  If there are multiple requests for the user's location,
> > then the return shape may be varied (as long as it still contains
> > the baseline circle).  If the user moves outside the baseline
> > circle, then you choose a new random baseline circle.   Example here:
> > <http://geopriv.dreamhosters.com/fuzz.pdf>
> >
> > This algorithm guarantees that all an observer gets by averaging/
> > intersecting is the baseline circle, which has the minimum required
> > uncertainty.  If the target is moving, then you can add enough
> > jitter to obscure this to some extent, and you don't run into
> > boundary issues (like you do with "rounding" or "fixed grid"
> > approaches).
> >
> > This kind of maps on the the "point+uncertainty" construct that's in
> > the current Geolocation API spec, if you make the mental equivalence
> > "point+uncertainty = circle".  In this analogy, the center of the
> > baseline circle is a random fixed offset from the real location, and
> > the returned points will cluster roughly around the baseline circle
> > (with uncertainty values big enough to cover the baseline circle.
> >
> > The civic fuzzing works by restricting the set of civic address
> > elements that are returned to a predefined set.  The draft defines
> > six levels (full, building, city, region, country, none); for
> > example, the region level includes the "country" element as well as
> > the "A1", "A2", and "A3" hierarchical elements.
> >
> > Hope this helps,
> > --Richard
> >
> >
> >
> >
> >
> >
> 
> 

Received on Wednesday, 24 March 2010 18:21:34 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Thursday, 22 March 2012 18:13:46 GMT