Master Lock Combination Cracking
I looked this up because we have a combination lock that I’ve forgotten the combination for. I remembered that this brand of MasterLock was trivially cracked in Stuyvesant — a fertile ground for the lock cracking meme to spread by wildfire. So, in this age of google and personal web pages, I found this by some guy at Harvard, possibly from Stuy or Bronx Science for all I know: Master Lock Combination Cracking
I didn’t realize the combination numbers were so simply related. Basically:
Get the last number. This can be found by pulling and wiggling the dial. There are twelve points on the dial that are “stop” points. Seven of these are fake ones: they’re the ones that stop between two tick marks. Of the remaining five, four of them are equal, mod 10. The remaining one is the last number of the combination. Note that older, banged around locks are trickier to crack, because the dial may have shifted, and the true last number may now fall behind two tick marks.
The first number is equal to the last number, mod 4.
The second number is (second number%4) = (last number%4) + 2.
This leaves a hundred possible combinations which can be brute forced.
There’s an alternate method available at this geocities link.
January 9th, 2003 at 6:29 pm
well i got a lock that i bought last year when i bought it last year i lost it and now i found it but i can’t remember the combination # and need help but the serial number on the the back is 8000433
March 14th, 2004 at 5:27 pm
I have a combination lock that I have forgot the combination to
the serial number is 638010.
Can you help me out
TIA
April 28th, 2004 at 8:01 pm
can u guys help me out too i dont remeber mine either can u help out?
the serial number is 909414
April 29th, 2004 at 9:44 am
Hi, folks. Giving me the serial number of your combination locks doesn’t actually help; this serial number doesn’t correspond to anything, as far as I know.
The only way I know to recover the combination of certain types of master locks is to go through the process of cracking it using the method outlined in this post. It’s a shortcut to trying every combination, but it still may require a good half hour as well as paper and pencil to perform.
Please don’t post comments asking me for help opening your locks. I can’t do anything about it.
September 10th, 2004 at 8:44 pm
i have a berretta gun box and i changed the combination so my little bro couldn’t get into it and now i forgot it. it isn’t the same as a master lock but i was wondering if you could help me, or if you know someone who could.
September 17th, 2004 at 9:11 pm
ur crackin code sucks
how come the school janitors can open a master lock by just the
serial number?
this stuff for nerds
ill find other and easy way to open this locks
September 2nd, 2005 at 9:12 pm
help me out my serial number is 8000304
September 20th, 2005 at 11:49 am
i forgot my # the serial number is 904219
September 20th, 2005 at 12:07 pm
Guys, as noted, as far as I know, the serial numbers don’t correspond to anything. You’ll have to go through the cracking procedure the open the lock. It’s not that hard: I did it in 30 minutes yesterday when I had to dig up a lock, since my new gym doesn’t have built-in locks.
The procedure at this Geocities site works well and discusses the inner workings of these types of locks. They do talk about serial numbers, but only in reference to the set of locks that can be attacked using their methods: the serial numbers don’t correspond to the lock combinations.