What is Steganography?

Figure 1. Photo with hidden image inside.

In the context of images, steganography is the hiding of an image (or other information) within another image. The “carrier image” can then be sent over an untrusted channel (e.g., published on the Internet), and only people that know that the hidden message is there will… read more

Submitted on 11 August 2019


This article is firmly in the category “All work and no play makes Jack a dull boy.”, so don’t take it too seriously… Do you know what an antegooglewhackblatt is? Well, an antegooglewhackblatt is… read more


Submitted on 18 May 2019

Mapping Bits to a Constellation

Figure 2. Bit mapping for QPSK.

Before information can be transmitted using a digital modulation scheme, the information bits have to be mapped to the constellation. Each point in the constellation is known as a symbol, making the full collection of symbols a kind of alphabet of the modulation scheme. For most digital modulation schemes… read more

Submitted on 6 May 2019

Langton's Ant

Langton's ant

Say that you have an ant that lives on an infinite plain with tiles that can be either black or white. The ant can move in the four main directions, and it keeps moving indefinitely, according to the following two simple rules… read more

Submitted on 29 April 2019

What is a Constellation Diagram?

Figure 1. QPSK constellation.

A constellation diagram is a diagram that shows how the information in a digital modulation scheme such as phase shift keying (PSK) is represented in a modulated carrier. This article is a bit of an experiment; instead of introducing the constellation diagram by simply presenting it… read more

Submitted on 25 March 2019

This Person Does Not Exist

Persons that don't exist.

The image below shows eight faces that were generated through a machine learning technique called a Generative Adversarial Network (GAN). The faces are completely artificial, and do not correspond to… read more


Submitted on 5 March 2019

What is an Analytic Signal?

Figure 1. Spectra of cosine (left) and complex exponential (right).

An analytic signal is a signal without negative frequency components. This might seem a strange concept if you’re not used to it, but analytic signals are used in signal processing, for example in modems for telecommunications. Let’s start from… read more

Submitted on 25 February 2019


I’m working on a series of articles on modems. It’ll be a loose collection of posts, and not a true multi-part article such as the one on tomography. Modem technology is not widely known and/or understood, even by a technical audience. However… read more

Submitted on 13 February 2019

One Code to Run Them All (Python 2 and Python 3)

Quite a while ago, I decided to do all my Python programming in Python 3 as much as possible. This is essentially always for the typically small stand-alone programs that I put on this blog. I did this to encourage people to use Python 3 for their own work, and to be future proof. Additionally… read more


Submitted on 26 January 2019


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