With the next version of this system the hardware and layout has changed somewhat, using a commercial handheld Geiger counter (GMC-320+) and its audio output as a generic input for any MCU.

This, according to Jonathan, is how it works, using the original version of the game: "Doom has a fixed 256-value random number table from which numbers are pulled by aspects of the game logic".

Researchers propose a True Random Number Generation (TRNG) using dark pixel values of images received from the CMOS image sensor to provide unpredictability to the passwords.