Video screenshot by Anthony Domanico/CNET

We like to think that safes are, well, safe and do what they're supposed to do -- protect the valuable things inside from would-be burglars. But a security duo out of Melbourne, Australia, has developed a cheap gadget that they say can crack most safes in no time, sometimes within minutes.

Luke Jahnke and Jay Davis built the device using 3D-printed parts and the Arduino open-source computing platform popular among makers, along with salvaged electronics that let the device spin through all the lock's possible combinations. Jahnke and Davis note that most safes are group 2 combination locks, which let users set a combination of up to three numbers. Typically, the locks come pre-coded with one of about 10 different default combinations, and most users stick with the default combo since lock makers make it pretty difficult to change the default code.

The current prototype -- which was displayed at the Ruxcon Security Conference in Melbourne last week -- can crack any group 2 lock combination in less than four days using automatic brute force attacks that run through all possible combinations. But if they loaded the 10 default codes on an SD card that they hook into the Arduino board, the prototype can crack pretty much any lock using a default code in just a few minutes.

And on the off chance that a safe you're trying to crack doesn't use a default code, the duo is working on building the device so it can pick up where it left off should you need to run away to avoid getting busted while trying to crack the code and come back to finish the job another time. "Not that we condone that," Davis was quick to point out.

You can watch the prototype in action in this video report by The Register.