Tag Archives: Combo Breaker

This Arduino-based device can crack a Master Lock in under 30 seconds

Think those belongings are safe in that gym and high school locker of yours? You may want to think again.

A few weeks ago, hacker Samy Kamkar demonstrated just how easily he could crack a Master Lock combination lock in less than eight attempts using nothing more than a simple mathematical algorithm. In the tail-end of his video, he also hinted that he had been working on an Arduino-based, motorized cracking machine that would be capable of doing all the legwork for him. The Maker said the device would be introduced in the very near future.


And well, the future is now. As a way to highlight a vulnerability in one of the world’s most ubiquitous brands of combination locks, the Maker has created a battery-powered, 3D-printed robot that can pop open any locker in as little as 30 seconds. Simply attach the aptly dubbed Combo Breaker to any of the countless Master Locks, turn it on and let it get to work.

“The machine pretty much brute-forces the lock for you,” Kamkar says.

When left on its own, the Combo Breaker can take upwards of five minutes to break open a lock. However, with a little help of finding the first number on the dial using Kamkar’s web-based tool, the process will take under a half a minute.


The Combo Breaker employs a small stepper motor to turn the dial, an optical sensor to keep track of how much the stepper motor is turning, a rotor with a 3D-printed attachment for the lock’s face, a lever that tries to lift the shackle, another sensor that can detect if an attempt to lift the shackle has failed, and an Arduino Nano (ATmega328) for the brains of the operation.

Want one of your own? Kamkar has provided a step-by-step breakdown of the build along with its required parts (which should cost approximately $100) on his site here. Meanwhile, you can find all of the necessary software for the machine on GitHub.