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Comment by drdrey | Hacker News Reader

I have it turned on, but honestly it's not very hard to figure out where I live... it's in the middle of that circle where my runs oddly seem to stop

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Don't center the circle on where you start your tracking. Create multiple overlapping circles to further obfuscate.

And ride / run through the circles on occasion. These will show up in tracing confusing the analysis.

Pro tip: You don't have to put the center of the privacy zone to your actual living location.

If you start and stop your run going different directions it's not too hard to figure out the central point between them, but if you start/stop from the same direction then it's not clear what the "middle" of the circle would be because the radius of the circle is configurable and unknown to viewers.

To expand on this, it takes three points to identify a circle, so you'd need to leave home and return from three different roads (at least at the intersection with the circle).

You can still potentially make useful inferences without 3 points. For instance, imagine the configuration where there is a single straight road that leads to your home (center of the privacy circle) - you can just extend the line where the GPS tracks for 5/8 mile (the biggest privacy setting) and infer the location of the home. Similarly, if you have 2 straight GPS tracks leading to your home, you can infer both the center and the radius of the privacy zone.

You may not get the exact street address, but you could definitely figure the block or the street. Maybe not super useful in a dense city, but that could leak quite a bit about you if you live in a suburb or rural area.

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