opening dial combo locks backwards?

[kstoerz]

Greetings; another forum noobie checking in here. I've played with pin-tumbler locks casually since middle school, but only recently have I begun to play with the link between math and combo locks. Here's a topic I haven't seen anything on yet; probably because it is 110% pointless with regard to opening a lock...

I always used the stereotypical Master padlock in high school, which opens right-left-right. I guess that this is not the de-facto standard, and there are plenty of locks that open left-right-left. Here is my thought: since all you are doing by turning the wheel is aligning three discs, wouldn't it be possible to create the same alignment by turning the wheel the wrong ways?

I tried a few things with my trusty Master padlock from high school (that I actually welded back together when a classmate had it snipped one time... me and this lock go way back) that opens right-left-right. First, I tried just putting in the combo with the wheel being turned the wrong directions. This naturally didn't work. Next, I tried reversing the order of the combo as well (fully expecting failure) and was not rewarded. I have had at least one master clone apart years ago to see what they were made of, so I have a good mental image of how the mechanism works (with the exception of exactly how the hasp's latch interfaces with the wheels), but I can't picture what would be necessary to correctly set the wheels in reverse.

Here is what I can figure:
Regardless of what happens, the backmost wheel is the first one to be dropped into place since it is at the end of the train. Since the dogs that connect the wheels inside have thickness, stopping at the same number from different directions will certainly result in the rear wheel being left in a different position. I guess the first step to figuring out this puzzle (without cheating and observing the wheels through the hole) would be to learn what the thickness of these dogs is and decide how many thicknesses stack up from a lefthand stop to a righthand stop of the same number on the wheel by the time the rotations make it back to the last wheel. The next wheel out should have less thickness-induced error, but I can't decide if it would be half as much or a different factor. Either way, if the thickness of these dogs can be translated into a numerical range on the dial, the work is probably cut out.

I'm well aware that this is a totally pointless exercise from a practicality standpoint, but the puzzle aspect of it has me fixated.

I also just read up on the somewhat infamous mathematical solution to deriving Master combinations. Using the modulus technique with a value of 4, I was indeed able to get 100 combinations of which one was correct.

I hate busy-work, so I wrote a PHP script to do it for me. Try it out if you desire, specifying the last number of the combo in the URL:
http://basementfreaks.com/members/karl/master.php?n=38

Any thoughts on the backwards opening idea? I guess I would consider success to include coming up with a way to calculate the reverse combo for a Master padlock. I also should note that this may not work at all if the lock depends on the correct rotation direction to engage the release mechanism or something. If the lock merely lines up the notches in the wheels, I don't see how it couldn't work.

[illusion]

Your idea is actualy genuine.

on the combo lock I have you have to turn the dial clockwise 2 full turns to the first number, then turn it anti-clockwise going past the first number to the second number... standard clockwise turning for the final number.

the combo normaly for mine is:
2 full turns clockwise to the first number - 34.
1 full turn to the second number going past the first, stopping at - 16
turning clockwise to - 24
pull shakel upwards

To do it the other way round gives me this result:
turning anticlockwise one full turn to - 27.
turning clockwise to - 20.
turning anti-clockwise to - 25.
pull shakle upwards

doing it the opposite way leads all the combos on mine to be between 20-30... these results are also consistant, and are only one digit off each time, irrespective of how the discs are placed prior to the dial being turned.

my combo lock is made by Squire, but it is really a copy of the master combo lock.

[DrStu]

The Reverse Combination for a MasterLock 1500 Combo is as follows.

Turn Left and stop at 6 less than the 1st number
Turn Right and stop at 3 more than the 2nd number
The last number will be the same

I got this from http://www.geocities.com/masterunlocked/

This website has a lot of good info on manipulating Master Combo Locks.

[kstoerz]

woot! Thanks, Illusion.

Based on what else I have read, my masterlock has tighter tolerances than most. I can't work the combination further than a half number away from the proper numbers, and I can only cheat it this far when the offset is all in the same direction of rotation it seems.

I tried your math on my lock, but with no luck. Looking at your numbers made a few connections for me, one of which is that you have to stop short of the "correct" number by a factor determined by the thickness of the dogs connecting the wheels. I turned my lock several times clockwise carefully, stopping on zero. listening and turning the other way, I felt/heard the first set of dogs engage the second wheel three numbers away from a full turn. Continuing, I heard the next set of dogs engage the front wheel at three more numbers short of a full turn. The measurement seems to be pretty exact at 3 marks, so instead of 7/4/1 (your differences in combinations), I tried 6/3/0 and it worked!

Basically, with a master combo padlock, you can open the lock backwards by stopping short of the correct number by 6 marks for the first number, 3 for the second, and by going all the way to the final number.

Anyone care to figure out what the offsets are for a different kind of lock?

[illusion]

Code: Select all

# 32 - 6 - 24
# 32 - 10 - 24
# 32 - 14 - 24
# 32 - 18 - 24
# 32 - 22 - 24
# 32 - 26 - 24
# 32 - 30 - 24
# 32 - 34 - 24
# 32 - 38 - 24

btw.. the script you wrote is actualy only effective on Master locks it seems.. my squire lock couldn't be opened with any of the combinations your script brought up (the closest ones listed above)... in fact it didn't suggest any beginning with 34.. so no luck using it for me.

I can be 1 number out each time... for instance 34 could be 33, or 35

This is why you ended up with different results turning anti-clockwise... your method would work on mine based on the looser tollerances of my lock.

So "Squire Locker-Lock"= 1 number tollerance on each side of correct combo.

You could have: 6/3/0, 7/4/1, or 8/5/2 difference on my lock turning it the opposite way round - all of which will work.

Very good thread mate

[devnill]

Thats really cool. I actually have been toying around with a similar idea. The combo lock on my po box ruens backwards from a master and it annoys the crud out of me whenever i try to open it ( i always go backwards), so i want to do the same thing. The only tough part is that it opens in a really odd way. when you get the last number, you ourn the dial backwards, and it opens the latch, but its on a sping, so you really need to grip at it. i tried to do it in reverse, but ive had no luck sofar

[media2030]

wow, that is really cool. i've thought of the idea before but never really pursued it. great thread