ffmpeg is a powerful command line tool for processing video and audio files. ffmpeg can do just about anything you can imagine with media files. The trouble is in understanding how to invoke the program correctly. There are a few options that require some Linux and multimedia expertise to get right. This article covers a couple handy ffmpeg hacks that have made much of the audio/visual content on this website possible....
The Ulam spiral is a graphical depiction of a set of prime numbers devised by the mathematician Stanislaw Ulam. To quote the Wiki, it’s constructed by writing the positive integers in a square spiral and specially marking the prime numbers. The outcome is a square with distinct diagonal, horizontal, and vertical lines. This post will walk through the development of a Ulam spiral visualization tool. Creating a Ulam Spiral Take a look at the 4x4 Ulam spiral below:...
The Caesar Cipher (CC) is a classic symmetric key algorithm dating back to the time of Julius Caesar. If you are new to cryptography, the Caesar Cipher is a great first crypto algorithm to learn. This post will walk through the details of implementing a CC encrypt/decrypt function. You’ll then get a look at the internals of a CC code cracker. Algorithm Description There are four key ingredients to a Caesar Cipher:...
Do you remember when you first learned about recursion? The thought triggered a memory from an old CS101 Java course. The textbook had some fractal triangle thing made with only 20 lines of code. At the time, it was a confusing 20 lines of code. A quick search on Google for “fractal triangle recursion” led straight to the Sierpinski triangle. A Sierpinski triangle generator with an ncurses visualization is a fun afternoon project....
If you’ve been around the open source community long enough, you’ve probably heard of people signing their VCS commits/tags. This post covers the why and how of signing your Git commits. The focus will be on commits but keep in mind that these tips equally apply to tags. Why Sign Your Commits The short answer is, signing your commits makes it harder for an attacker to impersonate you. Sure, if you work solo on rinky-dink toy projects, having your commits signed isn’t a big deal....
Do you have a bunch of dotfiles? Do you maintain a GitHub repo with all your dotfiles? Whenever you upgrade your machine, do you find yourself manually placing the dotfiles in the right spots in your home directory? If you answered yes to these questions, read on. Enter GNU Stow GNU Stow is a dotfile management utility. Stow has all the makings of a varsity athlete: Stow is small (a 32KB Perl script)....
If you grind old Advent of Code problems, you might notice a particular style of problem crop up more than once. The people of Reddit refer to their solutions as a variation of Conway’s Game of Life (GoL). Wikipedia has a great article on GoL. The animations are eye catching. The Wiki serves as motivation for a terminal app that visualizes GoL simulations. Rules of the Game What are the GoL rules?...
You ever come across one of those ASMR programming videos? This video where the developer programs a terminal display with a couple of spinning cubes is neat. This video is the motivation for the development of a ncurses application that renders a user controlled 3D cube. Perspective Projection and Rotation Matrices So how do you take an object in 3D space and visualize it in 2D space? The answer is perspective projection....
If you’re familiar with the kbhell application, you might realize that kbhell is about 90% of the way to being a keylogger. Why not finish the job and write a proper, cross platform keylogger that captures a victim’s every keystroke (for science reasons, of course)? The Requirements So there’s the obvious requirement of capturing user keystrokes. When you think about the fact that keyboards have different layouts, there are different language sets, etc....
Do you enjoy the sound of a mechanical keyboard? What if it was possible to achieve the sound of the keys clacking without having an actual mechanical keyboard? That was the idea that spawned this keyboard hell (kbhell) project. That and trolling friends by playing a soundbite every time they press a key! Getting Started When a user performs any keystroke, a audio file gets played. One of the main kbhell requirements is that it runs on both Windows and Linux....