ntang (ntang) wrote,
ntang
ntang

"Picking" master locks

I thought I had lost the combo for my master lock, so I went online and looked for instructions on how to "pick" them. I had friends in high school who were big into lock picking and I had seen one of them open at least half a dozen, so I knew it was possible.

Anyways, I did find the combo, but I also found a page that had the correct information. The problem is that there are multiple sites with instructions, and most of them are wrong and/or out-dated. But here's one that works:

http://www.dontforward.com/masterlock.htm

It's pretty interesting, actually. If you pull out the u-shaped arm and turn the lock, it will stick - in 12 places. Seven of these sticking points will be between numbers - 19.5, for instance. Five of them will be directly on numbers. 4 of these whole numbers will end with the same digit; one will be different. That one is the last number in your combo. (In my case, the numbers were 0, 36.5, 33.5, 30, 27, 23.5, 20, 16.5, 13.5, 10, 6.5, and 3.5. The whole numbers all end with 0 except for one: 27.)

From there, the rest is trial-and-error plus a bit of math.

The (last number modulo 4) = (first number modulo 4). So 27 % 4 = 3. That means the first number can be 3, 7, 11, 15, 19, 23, 27, 31, 35, or 39.

The (second number module 4) = (last number module 4) +-2, which means 3-2 or 3+1, either 1 or 5. So the second number can be 1, 5, 9, 13, 17, 21, 25, 29, 33, or 37.

At this point, now, you just have to brute force it.

The older locks were actually "pickable" just by knowing how they worked and being careful; by pulling out the arm and watching where it stopped, you could actually figure out all three numbers, but they were alerted to this and fixed it. Still, you can go through all of those numbers in 20 or 30 minutes if you're careful.

Anyhoo...
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