Technology

Encrypting Secret Messages in Pictures

This is a very cool (and somewhat technical) description of a simple way to use Mathematica to hide a secret message in an image file.

http://blog.wolfram.com/2010/07/08/doing-spy-stuff-with-mathematica/

The basic idea is that you erase the last digit (in binary) of each pixel’s “color channel”, and then use that spot to store part of the secret message. Given an image, you can then recover the secret message by looking at that last digit in each channel.

This process does change the image somewhat, but not in a way that the normal human eye (with normal viewing equipment) would ever notice. In the post, the author subtracts the adjusted image from the original:

To most viewers, the difference looks like this:

Only under extreme contrast can you actually see the real difference in the two. Here, we see the invisible ink reappear!

All that’s left is to decode the colors and read your message. But be careful–sending and receiving secret messages might get you some unwanted attention.

By patrick honner, 16 yearsAugust 17, 2010 ago

Computer Modeling of Gulf Oil Dispersion

This is an interesting computer simulation of the potential spread of the gulf oil disaster throughout the Caribbean and Atlantic:

http://www.youtube.com/watch?v=nAiG-TPYIFM

This reminds me of weather-prediction models: input some initial conditions, set up the propagation rules, and then iterate, iterate, iterate. Of course, modeling the mathematics of the initial conditions and the propagation rules is a huge challenge.

By patrick honner, 16 yearsAugust 14, 2010 ago

Representation Statistics Technology

Cool Representations of Data

This is an awesome demonstration of world-wide trends in life expectancy by Hans Rosling. The graph uses regions of changing size, location, and color to show the dynamic history of the data.

http://www.youtube.com/watch?v=QHCt6PmSs0k

I happened upon this here, where there is much more appreciation of Rosling, the “zen master of presenting data”, and his work.

By patrick honner, 16 yearsJuly 25, 2010 ago

Application Geometry Technology

Water Ellipses?

A funny thing happened on the way to the graphing utility.

I thought I’d use Geogebra to estimate the equation of the water parabola I saw at the Detroit Airport.

So I pasted the photo into Geogebra, dropped five points on the arc, and then used “Construct Conic Through Five Points”. The results are on the right.

Now the weird part: the equation is not a parabola, but an ellipse. I thought that perhaps I had done a poor job of selecting points, but no matter how I chose the points, the equation came up as an ellipse.

Note the presence of both an x² and a y² in the equation below.

Is this a limitation of Geogebra? Is this an anomaly caused by rendering the digital picture? Or is the assumption that the path of the water is parabolic faulty?