Re:Show HN: Anonymous messaging with a 1km radius
by rawnlq on Friday October 28, 2016 @02:04AM
(#12813489)
I am not sure if your original solution will actually work.
For example an attacker can just spoof enough accounts to sample from your distribution to figure out the true center. Imagine spoofing a grid of users with let's say K fake accounts per dot, then if you plot the histogram of who managed to connect you will see a very clear bump in the 2d histogram in the shape of circle.
The solution in your edit is much better.
Re:Show HN: Anonymous messaging with a 1km radius
by civilian on Thursday October 27, 2016 @04:52PM
(#12809978)
Heh, it's like salting their location.
Re:Show HN: Anonymous messaging with a 1km radius
by yarou on Thursday October 27, 2016 @06:37PM
(#12810967)
Believe it or not, but this is exactly what the Chinese government mandates. It's known as China shifting[0], and can cause quite a lot of headaches.
[0] https://en.m.wikipedia.org/wiki/Restrictions_on_geographic_d...
Re:Show HN: Anonymous messaging with a 1km radius
by bo1024 on Friday October 28, 2016 @12:38AM
(#12813134)
I'm thinking of ideas like [differential privacy](https://en.wikipedia.org/wiki/Differential_privacy).
That kind of thing combined with some rate limits (how often one can attempt to connect to a user) should be effective.
(edit) Actually, I think I like mseebach's suggestion even more: For each user, pick a random location about 100m away from them, then pretend they're there until they've moved far enough away, then repeat.