Automated Master Lock Crackers

master lock cracker

[xander] sent in links to two machines designed to solve padlocks automatically. The first one just modified an old robot project since it already had the necessary stepper motor. The second one was built from scratch and includes a solenoid to test the lock. Both systems are just brute forcing the combination, but they do use some shortcuts. Even though locks have 60 numbers there is less than 20 actual divisions. Also, multiple final numbers can be tested without putting in the first two. With these two shortcuts there are approx. 400 passes. These machines can solve a lock in about 30 minutes. Of course we’ve shown before that any human can solve one in about 10 minutes.

26 thoughts on “Automated Master Lock Crackers

  1. With the cheapo knock-off versions, you can even feel out the cams as they hit the right numbers. I used to play around with the locks in my dorm’s mail room that way. Just for fun, of course. No mail theft or anything, ’cause that’d be illegal and stuff.

  2. Actually, there are only 40 numbers–0 thru 39, and there are only 11 possible “notches”. I’ve disassembled a number of these master locks, and if somebody leaves the tumblers in the original position I can get one open in about 10 secs. If they don’t, there are only 11*11 (since on the third number you just try over and over at the 11 positions and it will suddenly open on one of them when you have the first 2 nums right already)–so 11*11=121 combinations you have to try to get one open. You can find the 11 notches by pulling down on the lock while its say connected to a locker and seeing where the wheel stops moving when pulling fairly hard–once you find another notch the next notch should be about 3 numbers away. You might think, oh my combination is 5-22-13, but actually you can do 6-21-13 or 4-23-13. (one number off up or down–effectively dividing 40/3=13). Since its not strictly that you can be off by 1 (you can actually be slightly off by more than 1) the number is 11. I’ve tried this while looking at the tumblers and its definitely true and used to impress my friends in junior high doing this. So if you have one of these locks that you’ve lost the combo on, just find the 11 notches–write them down, and start doing all 121 combinations. Odds are that you’ll solve it in less combinations–maybe closer to 60 tries. If you’re quick and precise you can do one try ever 15 seconds or so–so 15-30 mins you should have one open. I have had the unfortune of going thru all the combinations and not getting it–which sucks, but happens if you get sloppy.

  3. haha, well, didn’t realize that the other article was explaining how to do the same procedure I was talking about (I attest that it works)… well, the robot is cool–overkill for sure, and the other method I think is wrong–I think its 11 notches not 10. But maybe my memory is wrong on that… anyway…

  4. I remember making one of these out of Lego Mindstorms I received for my thirteenth birthday… of course, since it was Legos, it wasn’t precise enough to actually record the final combination — but it did use the shortcuts outlined above.
    Worked once, but some pieces broke in sheer surprise (the motor/gear system was pulling too hard for its own good, and parts snapped when it jerked back with no resistance ^o^)

  5. yea i thot it would i was just being lazy

    cool hacks i’ve always been into the actual physical undermining of supposedly secure things.. although i could never get that bike lock pen thing to work soooo i dunno.. and my kryptonite lock has an actual key shaped key thank god.. sorry off topic.

  6. with the 11 nothces, only 6 of them will be exactly on a number, the rest will wiggle between them. YOu have to get those 6, and they will all end in the same number except ONE, and that one will be the last number of the combination. so you usually get something like
    5, 15, 25, 28, 35
    28 is the last number of the combo

  7. Talk about brute-forcing: 10 years ago in high school there was a 1-second solution: take off your sneaker, grab it by the toe and bash the top of the lock with the heel.

    Not very elegant, but that’s how most of the lockers were broken into (I was never brazen enough to try on anyone’s locker but my own).

  8. chuck, we would just kick the bottom of the locker and pull hard on the lock. One kick and i could be in half the lockers in the school. I never used my combination because it took too much effort. I had forgotten it by the end of the year.

  9. Even faster then the code cracking method (but not quite as fast as the bolt cutters which leave the lock useless or the shims which don’t recover the combo) is to take a pair of diagonal wire cutters or a decent pair of pliers and peel up the lip around the back edge of the lock. It is just thin sheet metal, with practice they come off in about 30 seconds. Then the lock falls apart. From there you can pull out both combo wheels and put it back together as a one-combo lock (just turn to the right number and pull), put one wheel back on for a 2 combo lock (works great for most applications where you don’t expect someone to try to brute force it) or all 3 for a complete lock. I takes about 5 minutes for me to take one apart/put it together.

    I really find it surprising that no one figured that out before I did (or if they did they haven’t published it anywhere I can find)

  10. I think it was in the book “The Watchmen” about the phreak/hacker kevin poulson where he talks about freezing a telco padlock with a spray can and then breaking it off with a hammer…something about freezing stuff just makes it more james bond-y.

  11. Dont get me wrong this is definitely one of the cooler hacks on Hack-a-Day in a while, but I think its a little bigger then it needs to be. I dont think it would be all that difficult to make the same device that could easily fit into say a box that could almost fit into your pocket. Im not really one for mechanics but I believe all you would need is a two way motor and some good code, and a power source. I think it would be pretty cool to just slip it over a lock let it pop ‘r open and then have the combo. Anyone here up to the challenge? I can’t do the physical build but i can make the brain work. Drop me a line

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