Imagine you need to move a file between two devices, but there's no Wi-Fi, no Bluetooth, and you're in a high-security environment where air-gapping is the only way to stay safe. Enter Decimen Optical Transfer, a clever proof-of-concept that turns your screen into a high-speed data projector and your camera into a receiver.
The Magic of Fountain Codes
Traditional file transfers are like a conversation: "I sent part 1, did you get it?" If a packet is lost, the whole process stutters. Decimen flips the script using Luby Transform (LT) fountain codes. Instead of sending sequential chunks, it treats data like water from a fountain. The sender streams an endless sequence of encoded QR frames.
The receiver doesn't need every single frame—it just needs to collect enough of them (roughly 1.15 times the original file size) in any order. If the camera misses a few frames due to a glitch or a shaky hand, it doesn't matter. There is no need to restart or request a re-send; the receiver just keeps collecting until the file can be "peeled" back together.
Browser-Based and Air-Gapped
What makes Decimen particularly impressive is its accessibility. Built with the help of Claude Code, the system operates entirely within a browser. There are no apps to install and no pairing processes to navigate. By leveraging browser-native APIs, it achieves claimed speeds of up to 128 KB/s—fast enough to move text and small files through a series of rapidly flashing QR codes.
While it's currently a proof-of-concept, the implications for secure, unidirectional data transfer are significant. It proves that you can move meaningful amounts of data through a physical gap using nothing but light and smart mathematics.
As we move toward a world more concerned with privacy and air-gapped security, Decimen shows us that sometimes the best way to connect two devices is to stop trying to network them entirely.
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