19 Can the combination of a Master Lock be found though manipulation?
Description
This article is from the Locksmithing FAQ, by Joe "Spike" Ilacqua spike@indra.com and Henry Schaffer hes@ncsu.edu, major data collection effort by Scott Anguish sanguish@digifix.com with numerous contributions by others.
19 Can the combination of a Master Lock be found though manipulation?
Recently a method of finding the combination of a Master Lock has been
presented on alt.locksmithing. It seems there is a formula that
relates the numbers in a combination to each other. The first and
last digit of any combination will both have the same remainder when
divided by 4, and the second digit's remainder when divided by 4 will
be - or + 2 from the first and third's remainder. For example, if you
knew the last digit of the combination was 5, the first digit could be
any digit that had a remainder of 1 when divided by 4 and the second
number any digit with a remainder of 3 when divided by 4. This means
given one number in the combination, there are only ten numbers that
can be in each of the other two positions, and thus only 100 possible
combinations given one number in the combination.
This "modulus 4" constraint does not appear to apply to "current"
production locks (1999?-).
And it turns out there is an easy way to find the last digit of the
combination. On older Master Locks, ones where the arrow at the top
is raised, simply pull on the shackle and turn the dial until it
catches, that's the third number in the combination. On news locks
with the recessed arrow, there are twelve places the dial will catch
if you turn it while pulling on the shackle. Seven of these will
catch between two numbers, ignore these, and find the the five that
catch on a number. Four of these will end in the same digit, i.e, 1,
11, 21, and 31, the fifth end with a different digit, and the is the
third number in the combination.
This means that given the knowledge, time, and patience, anyone can
find the combination and open your lock. But then so can anyone with
a pair of bolt cutters, a hacksaw, or maybe even a hammer. These are
three (US) dollar locks. They have many useful applications, but they
are not high security locks. Plan your usage accordingly.
_PLEASE_ don't post a question on alt.locksmithing
giving a serial number and asking for the combination for that
lock. Yes - there are books relating the two - but very few people
will take you at your word that it is your own lock. Instead the
most likely result is the start of a flame war!
Continue to:
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