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Writing mostly about computers and math.

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A house address.

Original image from Michael Carian on Flickr. Some rights reserved: cc by-sa.

If you use Tor then you've probably noticed that some .onion sites have addresses that don't look totally random, like facebookcorewwwi.onion or demonhkzoijsvvui.onion. Tor addresses are supposed to be randomly-generated — how do these have words in them?

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Some onions.

Original image from Thad Zajdowicz on Flickr. Some rights reserved: cc by.

Tor hidden services are useful for protecting privacy, but Tor users still have to rely on exit node operators to pass traffic from the Tor network to the web. Tor hidden services are designed to allow people to share websites with each other without either party revealing too much information about themselves. Another benefit of hidden services is that users can access them without going through an exit node, a weak point in the network's privacy protection and a resource with limited bandwidth.

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My favorite Rubik's cube

I got the idea in my head the other day to write a Rubik's cube solver. While working on that I accidentally learned some interesting math that I thought might be nice to share. Here, then, is a brief, probably over-simplified introduction to group theory and its applications to Rubik's cubes.

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Some pretty triangles.

A few months ago I was playing around with Delaunay triangulations and realised today that I never wrote anything about it. Briefly, a Delaunay triangulation of a set of points is a way of drawing triangles connecting those points in order to maximize the minimum angle of all of the triangles. They often look something like this:

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I got an Arduino Uno for Christmas this year and I've been playing around with it a little bit over the last few days. While trying to get a simple PWM program to work, I noticed that it starts acting weird at higher frequencies. The square wave actually produced by the microcontroller drifts farther and farther away from the expected signal the higher the frequency gets. Here's some oscilloscope output to show you what I mean. All of the signals should be 5 Vp-p and have a 50% duty cycle. The scope is set to 5V/div in every image.

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