Fitting Snake Into A QR Code


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.

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, it’s 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.

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.

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.

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.

QR codes are a 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.

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