QR codes are usually associated with ASCII text like URLs or serial numbers, but did you know you can also encode binary data into them? To demonstrate this concept, [MattKC] embarked on a journey to create a QR code that holds an executable version of Snake. Video after the break.<\/p>\n
As you might expect, the version 40 QR code he ended up using is much larger than the ones you normally see. Consisting of a 171 by 171 grid, its the largest version that can still be read by most software. This gave [MattKC] a whopping 2,953 bytes to work with. Not a lot of space, but still bigger than some classic video games of the past.<\/p>\n
To start, he first wrote Snake to run in a web browser using HTML, CSS, and JavaScript, which was able to fit in the available space. Modern browsers do a lot of the lifting with built-in features, and [MattKC] wanted more of a challenge, so he decided to instead create a Windows executable file. His first attempts with compiled C code were too large, which led down the rabbit trail of x86 Assembly. Here he found that his knowledge of Assembly was too limited to create a small enough program without investing months into the project. He went back to C and managed to compress his executable using Crinkler, a compressing linker commonly used in the demoscene. This shrunk the file down to 1,478 bytes.<\/p>\n
Zbar, a command-line barcode reader for Windows was used to test the final Snake QR code. [MattKC] discovered a bug in Zbarcam that prevented it from reading binary data via a webcam input, so through the power of open source, he submitted a bug fix which is now integrated into the official release.<\/p>\n
All the files are available for anyone to play with on [MattKC]s website. The video below goes into a lot of detail on the entire journey. Since this project proves software can be embedded in QR codes, it means that malware could also be hidden in a QR code, if there is an exploitable bug somewhere in a smartphone QR reader app.<\/p>\n
QR codes are an interesting tool with a variety of uses. Take a deep dive into how they work, generate a 3D printable version, or build a QR jukebox, if you want to learn more.<\/p>\n
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