Index Home About Blog
From: Doug Gwyn <>
Subject: Re: Locks was(Re: Pre-schoolers: )
Organization: U.S. Army Ballistic Research Lab, APG MD.

In article <> (Julius
Chang) writes:

#If it were me, I wouldn't depend on a Master combo lock for
#firearm security.  The older Model 1500 locks can be opened
#via dial manipulation as fast as if you already had the
#combination.  I easily popped one in about 15 seconds.
#The newer Model 1500 locks are vulnerable to a different
#form of manipulation attack and will yield within a few minutes.

Yup.  Amazingly, even government S&G "high-security" padlocks
(at least the ones in use some 20 years ago) could be *easily*
opened in seconds by anyone knowing the trick, and I once got
my class into an equipment vault/classroom through one of those
locks simply through manipulation (but since the instructor had
already called for security staff to come to our aid, I had to
relock it before help arived so we wouldn't get into trouble --
how's that for a system!)

#Forget about resistance to physical attack.

I think when the issue is in protection against inquisitive
children in one's home, bolt-cutter and other similar attacks
aren't likely to be of much concern.  It's the low resistance
to not especially clever attempts to open the lock that would
be most important.

A *key operated* padlock with positive shackle locking, such
as the old American double-ball-locking round-case padlock,
is fairly secure against children who are not versed in lock
picking.  Of course it won't do much good if you keep a key
where they can find it.

Date:	Wed, 29 Aug 1990 02:36:00 -0400
Subject: cheap Master combo lock

For "locker" style Master combo locks, you can probably doe the
combinatorics of the "soft spots" on it in under 10 minutes.
Some of the newer ones seem to have an extra mechanism to make it harder
to detect these points.... I've taken to actually writing down my combo
with these as it is such a pain to discover the combo from
experimentation...  Even so, the right answer is to figure out the combo
rather than use any of the cruder methods you listed.


Date:	Wed, 29 Aug 1990 03:24:00 -0400
From:	bgsuvax!
Subject: Re: cheap Master combo lock

There exists a book that lists all of the combinations by serial
number.  Many locksmiths have this book.  If you can demonstrate that
you own the lock, they may look it up for you.  I find it scary that
the relationship exists.

Personally, I prefer to use key locks with the serial/key number
written in ink (I erase the number) or to use locks for which I set
the combination.  At least someone can't look up the number in a handy

William C. DenBesten   is  or   denbesten@bgsuopie.bitnet

Date:	Wed, 29 Aug 1990 03:46:00 -0400
From:	Homer <CTM@cornellc.bitnet>
Subject: Re: cheap Master combo lock

     When I was a kid, a fellow camper showed me how to crack the
standard everywhere present master combo lock.

     Basically the idea was to find the first number by pulling
the shank out and turning the knob.  It would click or stick or
feel different at the place that corresponded to the first

     The third number was easy to find, assuming you had the first and
second number, all you had to do was turn the dial until the shank pulled

     Finding the second number was a matter of trying each one, not
that many.  It made it even easier in that the second number was
'accurate' only to 2 digits, so you only had to try every other
position to get the right one.

     I opened many a master lock this way.

Date:	Wed, 29 Aug 1990 10:56:00 -0400
From:	"William F. Wurzbach" <>
Subject: RE: cheap Master combo lock

        I had the same problem about a year ago and the solution was painless.
Go to the nearest hardware store that handles MasterLock locks. Explain to
someone there ( I approached the key-making department ) what the problem is,
get the address of the nearest MasterLock outlet or corporate headquarters,
and write a letter to them, explaining who you are, what the serial number of
the combination lock is, and giving the full address of the hardware store
you have made accommodations with. MasterLock will send the combination to
the hardware store ( authorized dealer ), where you can have them call you
or stop in periodically to check if it's arrived. No problem if you've got
the time.

Date:	Tue, 11 Sep 1990 00:18:00 -0400
Subject: Re: cheap Master combo lock

Use the hacksaw.  If it's a cheap Master lock you should be able to cut
through it in under five minutes.

The Polymath (aka: Jerry Hollombe, M.A., CDP, aka:
Head Robot Wrangler at Citicorp(+)TTI             Illegitimis non
3100 Ocean Park Blvd.   (213) 450-9111, x2483       Carborundum
Santa Monica, CA  90405 {csun | philabs | psivax}!ttidca!hollombe

Date:	Thu, 18 Oct 1990 21:00:00 -0400
Subject: Re: cheap Master combo lock

It used to be that there were only 100 possible combinations for those
locks, relative to the final number which could be easily determined.
A skilled person (such as a typical high school student) could run
through all 100 in under 5 minutes, using a simple trick.  In high
school I saw this technique used to borrow a locked ladder to
retrieve an errant ball from the gym roof!  This was in the early 70's.

Did Master ever improve this?


Date:	Thu, 18 Oct 1990 22:22:00 -0400
From:	nancy!wsrcc!
Subject: Re: cheap Master combo lock

>Use the hacksaw.  If it's a cheap Master lock you should be able to cut
>through it in under five minutes.

Five minutes?  You can pick a Master (keyed) padlock in 1/5 that time.
They are only 4 pin locks, and the pins are so sloppy that they make a
great "learning" lock.

The reason that Master's pick so easily is that they made an
interesting (but poor, in my opinion) design decision.  The Master's
I've seen have a two diameter top pin.

	cylinder split end

		 | |
		|   |
		|   |
		|   |
		|   |

	      Spring end

The reduced diameter section makes you pick the pins twice.  This
means that for a four pin lock you must pick the equivalent of an
eight pins lock.  This is good.

The problem is that the first stage picking is trivial - the reduced
diameter section is so tall compared to the normal tolerance of a
split.  The second stage picking is aided by the pin itself.  It stops
moving up when you get to the right place.  Good grief.

The moral, buy a real lock for anything you want to secure.  Often one
can re-pin a cheap lock with mushroom pins or pins with a set of kerfs
cut in them to thwart picking.  If customers stop buying junk like
master padlocks, then we will see a growing trend towards locks that
really work.


Wolfgang Rupprecht    uunet!{nancy,usaos,media!ka3ovk}!wsrcc!wolfgang
Snail Mail Address:   Box 6524, Alexandria, VA 22306-0524

Date:	Thu, 8 Nov 1990 05:00:00 -0500
From:	Gregg Grosshans <AGME003@unlvm.bitnet>
Subject: Re: cheap Master combo lock

In our campus rec locker room, all lockers are required to have a campus
rec lock on them, they are the Master locks with the otional keyed facility
on back to allow a master key to unlock any of the locks.  Are these locks
just as vulnerable as to what was described above?  What are the name brands
of "GOOD" locks?

Gregg Grosshans

[Moderator tack-on: The administrators of my old high school were not
particularly amused to discover that my key to same worked better than
theirs did...   _H*]

Date:	Wed, 23 Jan 1991 19:55:00 -0500
Subject: Reply to Re: cheap Master combo lock wanna talk vulnerability of a Master combo lock?  Sure, they
are vulnerable, but when you go and add that "Master Key Feature" to the
thing, then you really have problems.

All one has to do to have access to EVERY lock in the room is
a) Acquire the key from someone who has it (e.g: locker room attendant)
b) Manufacture a key (not too tough for an engineering student with some
   locksmithing ability in the area of impressioning...)

I hated those locks when I was in High School for the above reasons, and
protested vehemently against being forced to utilize a lock which the
school could open at will with no trace of such action ever being taken.
The result of such protesting being that one now has the "option" to bring
ANY lock which will fit thru the hole on the locker hasp, although the school
still does offer the option to rent the lock from the school for those who
often forget their combination....(and in my opinion -- such morons deserve
the feature)

...Bring your own lock!
bye for now but not for long

Index Home About Blog