The World in Miniature

Like many kids of my generation, I spent countless hours in the world of analog model railroading. But for me, it wasn’t just about watching a locomotive circle a loop of track. The real magic was in the creation: assembling plastic house kits, meticulously crafting terrain, and the complex “under-the-table” work of wiring up lights and electromagnetic turnouts. It was my first introduction to engineering and project management, though I didn’t know it then.

Following up on my previous post about Bridging the Gap: Bringing Modern Kismet to OpenBSD, it is time to explore the hardware that makes much of this wireless exploration possible. If you have a spare USB port and a €50 RTL-SDR dongle, you can turn your OpenBSD box into a powerful radio scanner.

What is SDR?

Software Defined Radio (SDR) shifts the heavy lifting of radio signal processing from dedicated hardware circuits to software. Traditionally, if you wanted to listen to a new frequency or decode a new protocol, you needed a specific physical radio. With SDR, the hardware is simply a “dumb” front-end that digitizes a chunk of the RF spectrum; your CPU handles the demodulation and decoding.

For years, OpenBSD was stuck in a technical time-warp. While the rest of the world moved to Kismet “Newcore” - with its powerful web-based UI, distributed capture, and multi-protocol support—the OpenBSD port remained anchored to the legacy ncurses version.

The core software, with some small patches, compiled fine, but there was a massive void: no Wifi capture driver for OpenBSD. To move forward and finally retire the ancient version, I had to build the engine: capture_openbsd_wifi.