Combo Lock Question

[Pickety]

All day today i've been reading about master combo locks and ways to crack/open them. The most common method described is by pulling on the shackle while turning the dial to find the 12 stick points and eliminate the fake stick points to get the last number and figure out the rest from there. Well i got out my newest Master lock and tried it. Heres what i came up with for the 12 stick points
2, 5, 8.5, 12, 15, 18.5, 22, 25, 28.5, 32, 35, 39

Well i've been reading that your supposed to come up with 7 numbers that are .5 and eliminate them as they are fake. But as you can see i've only come up with three. Well i decided to keep going, so i crossed out the .5's and im left with 2, 5, 12, 15, 22, 25, 32, 35, and 39. And thats where i got confused... the actual combo to my lock is 18, 20, 38. None of the stick points matched any of my actual combo numbers.

I played with the lock numerous times for the stick points and they always come up the same. Those stick points are the result from pulling on the shackle and turning the dial clockwise...i tried doing it counter-clockwise but still nothing good happened. Does anybody have any ideas or advice about this?

[strazzere]

Pickety,

I'm not sure which place you were reading about the combo locks... However try reading this artical. It's worked fine for me on every lock I've tried...

http://www.fusor.us/lockpick.html

(taken from hackaday.com blog link)

Also - do you need the combo? Or just trying to unlocking it because... Shims work a lot better in my opinion... No unneed math - but thier are some programs people wrote to do the math for you if need be.

Hope that helps

[Pickety]

Well with the lock that im practicing on i already know the combo, im just testing out methods that are used to open them when you dont already know the combination. I do agree that shims usually work better, but im just tring to get into cracking them because i've really only focused on picking locks before, but now im gonna start getting into combo locks.

I just finished reading that article and ill try it, but i just need to know, do you do this method by turing clockwise, or counter? (i only ask because some articles say to crack it clockwise and some say to go counter clockwise)

[sportsguy]

Great article! Not that I fully grasp it, but I'll give this a go tonight on an old combo lock wich I no longer have the combo for. We'll call it Patience practice rather than cracking...LOL

I'm sure I'll fail, but at least I'll become more familiar with the concept and math behind it.

[sportsguy]

Happy to say that I actually figured that all out last night. I figured out the last # in the combo (and was right), figured out the 2nd #, figured the possible combinations and am now happily spinning them off to reach the goal. Probably finish it tonight in my spare time.

Great info, great article, well written and accurate - if you read it carefully.

Thanks.

[E-Mind]

So, I was bored and decided to write some code to do this calculation for me - hope someone finds it useful (I couldn't find code for this online - the one link I found was dead)

Code: Select all

#include <stdio.h>
void main() {
   int First, Second, Last;
   
   printf("Enter last number of combination: ");
   scanf("%d",&Last);

   for (First=0; First < 40; First++)
      if (First % 4 == Last %4)
         printf ("First number could be: %d\n", First);

   for (Second=0; Second < 40; Second++)
      if (Last % 4 == (Second % 4) + 2)
         printf ("Second number could be: %d\n",Second);
}


FOR THE REEEALLLYYYY IMPATIENT

1. The 'user' finds that the third number is 17

2. The 'user' turns the dial clockwise several rotations, until he is moving all three disks. (you can actually feel when the second disk begins rotating, and the first)

3. The user continues turning clockwise and stops on the number 1, his first guess for the first number.

4. The user then begins turning the dial counter-clockwise slowly, until he feels the third disk (for he is directly turning the third disk) collide with the second disk. (Which should happen around 0 or 39, in this case)

5. The user rotates the second disk to the 3 position, his/her first guess for the second number.

6. The user then rotates the dial (and the third disk) to the predetermined 3rd number, 13.

7. The user pulls on the latch. Assuming it does not open, for that would prove to be boring, the user continues as such:

8. The user SLOWLY, rotates the dial counterclock wise until he/she feels the second dial, at the number 3 where he/she left it.

9. The user rotates counterclockwise from 3 to 7.

10. The user then rotates clockwise back to 13.

11. User pulls latch.

12. user rotates counterclockwise till the user hits the second dial at 7, and pushes it to 11.

13. user rotates clockwise back to 13.

14. user pulls latch.

http://www.totse.com/en/bad_ideas/locks_and_security/166220.html

There seems to be an impossibilty for the last number to be '17' due to 17 modulo 4 is '1' and not '3' as quoted from the article.
the reason he wrote '3' was because he was treating '17' as a hexadecimal number (base 16) which is '23' in decimal (base 10) and '23' modulos '4' is '3'. He probably typed it into visual-studio debugger's watch - and had it set to show the values as hex.

Since it is '1' and the second number needs to have a negative modulos (due to adding of 2) == not possible.

[E-Mind]

Here is a list of number that can not be the third number of the combination:

Third number can not be: 0
Third number can not be: 1
Third number can not be: 4
Third number can not be: 5
Third number can not be: 8
Third number can not be: 9
Third number can not be: 12
Third number can not be: 13
Third number can not be: 16
Third number can not be: 17
Third number can not be: 20
Third number can not be: 21
Third number can not be: 24
Third number can not be: 25
Third number can not be: 28
Third number can not be: 29
Third number can not be: 32
Third number can not be: 33
Third number can not be: 36
Third number can not be: 37

Here is the code that produced this list:

Code: Select all

   for (i=0; i < MAX_NUMBERS; i++)
      if (i % 4 == 0 || i % 4 == 1)
         printf ("Third number can not be: %d\n",i);

[E-Mind]

so basically -
the first and second numbers can only be of these two sets:

First number could be: [2,6,10,14,18,22,26,30,34,38]
Second number could be: [0,4,8,12,16,20,24,28,32,36]

or

First number could be: [3,7,11,15,19,23,27,31,35,39]
Second number could be: [1,5,9,13,17,21,25,29,33,37]

The last number needs to be in the same set of the first number.

I hope this makes it easier now

[E-Mind]

So now you don't need a calculator - just look at that table I posted, and find the set of first numbers that your last number resides in - and you have the 10 possibilities of first and second numbers.

since there are only 10^2 == 100 possible combinations of first and second numbers for a specific last number - Following the 14 steps quoted would get you the combination quickly with ~100 turns of the dial.

[E-Mind]

here is an easy way to memorize it:

Code: Select all

-Cracking Master Combination Locks-
The first number is in the same set of numbers as the last number.

    Second number set #1:  [00,04,08,12,16,20,24,28,32,36]
    Second number set #2:  [01,05,09,13,17,21,25,29,33,37]
Last/First number set #1:  [02,06,10,14,18,22,26,30,34,38]
Last/First number set #2:  [03,07,11,15,19,23,27,31,35,39]

Too much time wated on this

[E-Mind]

actually I take this back -

The second number modulus 4 is the last number modulus 4 plus or minus 2.

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

I thought at first it was just minus 2.

so - the table is:

Code: Select all

-Cracking Master Combination Locks-

Last number set #1:  [00,04,08,12,16,20,24,28,32,36]
Last number set #2:  [01,05,09,13,17,21,25,29,33,37]
Last number set #3:  [02,06,10,14,18,22,26,30,34,38]
Last number set #4:  [03,07,11,15,19,23,27,31,35,39]

 -The first number is on the same set as the third number.
 -The second number is two sets bellow or obove the set of the first/last number.

If the last and first numbers are on set #1 or #3, the second would be on set #3 or #1 respectively, and if the last and first numbers are on set #2 or #4, the second would be on set #4 or #2 respectively.


[rayman452]

how do you use code?

[E-Mind]

compile it in a C compiler lol

[strazzere]

visual basic program (from original artical): http://www.fusor.us/programs.html

Mac APP using real basic: http://homepage.mac.com/joshpeek/masterlockcracker.html

cgi (web) version: http://www.dfw.net/~scottvr/crackmaster/

just a quick search and i found all those.. I have a version in C i use on my pocketpc... and theirs also a "rumor" out there that someone made a program on a ti-83 to do it, which is pretty nice/funny