Security Flaw- Master Lock 1547DCM

by **lockedin** » 13 Sep 2006 1:52

Ok, ok-- this is nowhere near the level of a Tobias discovery, but I'm pretty proud of my observation.

So my girlfriend got me a Master Lock combination lock for my back pack along with other gifts for my birthday (she knows I like to locking everything up). I told her I would find a bypass soon.

The next day I was applying tension while turning the dials seeing if it would stick on a certain number (a common security flaw in many combo locks with dials). This wasn't working so well. Luckily, I observed that under the dials were some green rotor things with bumps on the edges (pictured below). At the correct numbers there are two bumps with a bigger separation than the rest. So I changed the combination, and wa-lah, the same thing. I wowed her later when I told her to change the combo, mix it up and give it back to me.

So the key is to get all three rotors so that the bumps with the biggest space between them is visible to you. Sorry for the blurry pictures, my camera is kind of sorry for up close pictures.

by **Schuyler** » 13 Sep 2006 9:32

Very cool!

Any discovery is a good discovery

Nice work.

by **picpower** » 13 Sep 2006 11:15

Good observation!

by pH » 13 Sep 2006 12:52

Thank you so much for posting this. I was preparing a post about the same lock, but now I can just put it here and don't have to take the photos

I was actually looking for a way to disassemble this lock so I could figure out how it works. I work out at a rock climbing gym and this is a very popular lock because it is kind of like a Carabiner, which is a tool we use in climbing. About a week ago my friend's lock failed to open when he put in the correct combination. I attempted to shim it by cutting up a this piece of a aluminum through the holes near the "shackle" part, but without knowing how the lock works I was unsuccessful. We eventually conceded and got the employees to go find the bolt cutters.

I still have the cut up lock and try to open it with your technique

by **Schuyler** » 13 Sep 2006 22:26

So!

I went out and bought this lock.

Awesome.

There is a bit of a flaw in this method, however, as mine wasn't lined up exactly the same as yours, however, the wheels DO all have to be turned in the same direction, which reduces the possible combinations of this lock to

(drumroll)

10!

hahahaha

Anyhow, hi-five on this one, man. Hopefully someone will actually publish this finding...or maybe you should?

Anyway, these locks shouldn't exist, not with such an obvious, easily exploited flaw.

10 combinations!

by **lockedin** » 14 Sep 2006 1:37

Schuyler wrote:So!

I went out and bought this lock. Awesome.

There is a bit of a flaw in this method, however, as mine wasn't lined up exactly the same as yours, however, the wheels DO all have to be turned in the same direction, which reduces the possible combinations of this lock to

(drumroll)

10!

Really?! Hmm.. yeah maybe it was the way mine was constructed. That sucks-- it worked so perfect. Well, I guess narrowing it down to ten isn't bad.

Thanks for double-checking Schuyler.

by **cL4y** » 14 Sep 2006 6:46

MAN this lock looks so WEAK! UHHH I JUST WANNA destroy it with my hands! *cough* sorry about that,i just feel like this locks can be torn off.

My friend and school had one of these,and we tore it off his locker with minimal effort,as there is about a 2mm space at the shackle (or whatever it is).

So we lined it up,and BAM, pull, snap, peg at the wall, crack, and i take the pieces home

And nice work finding the flaw,but i don't see why many people what consider this "security" i consider it "the B**ch of all locks"

by **Schuyler** » 14 Sep 2006 12:33

Wait!

Update.

There are, in fact, 2 ways to decode this lock, depending on the light offered by your environment.

Your way does work perfectly! I was only able to clearly see the bottom of the green discs, which have a large gap at one point, which all must be lined up alike (facing to the right) in order to open.

On top of the green discs are the notches/ridges you mentioned, I had not seen them before because the angle I had mine at didn't immediately reveal them.

My ridges lined up exactly the same as yours did.

So, 2 methods of decoding this lock, so far both exactly the same (check the bottom of your green discs so we can verify, if you have it laying around)

woot!

I'll try to borrow the girlfriend's camera to take some clear macro shots tonight.

by **lockedin** » 15 Sep 2006 2:28

So my trick does work. Good.

It would be really cool if you could get those macro shots up.

by **picpower** » 15 Sep 2006 8:10

I tested your bypass and it worked on the one I had.

Worked great!

by **Schuyler** » 15 Sep 2006 11:12

lockedin wrote:So my trick does work. Good. It would be really cool if you could get those macro shots up.

Unfortunately I'll be gone for the weekend and I've been working on my girlfriend's apartment this last week so no photos yet, but I'll get them done. (though I did find time to disassemble an old medeco mortice lock I had laying around

). Has anyone disassembled one yet?

by **lockedin** » 15 Sep 2006 15:01

Sadly, I have yet to get my hands on a Medeco (it's all the ebay snipers).

by **illusion** » 15 Sep 2006 15:09

I've taken apart a Biaxial mortice cylinder.

Luckily it had those snazzy little allen key screws above the pin chambers which made it a snap to take apart.

I did lose one of the springs for the sidebar, but manged to replace it with another spring I had spare - works perfectly. Used one I had from a tubular lock I took apart ages ago.

by **Schuyler** » 15 Sep 2006 15:26

illusion wrote:I've taken apart a Biaxial mortice cylinder.

Luckily it had those snazzy little allen key screws above the pin chambers which made it a snap to take apart.

I did lose one of the springs for the sidebar, but manged to replace it with another spring I had spare - works perfectly. Used one I had from a tubular lock I took apart ages ago.

Yar, I wanted to get it without using those screws, and actually managed to shim 3 of the 6 pins, but the third driver wouldn't catch atop my shim and finally managed to dent it up so badly it was no longer effective, so I went ahead and unscrewed my way to victory

Very cool locks. This one wasn't biaxial, but I have one of those as well, that I may take a shot at eventually.

And how much did they cost you ask? $1 each. I got a big lot of random locks (most of them sans keys) and found my DOM in there and my 3 medecos. Also some cool high security wafer locks. All in all, however, I took WAY too many cam locks. :\ but I was still happy with my few gems.

by **Krypos** » 15 Sep 2006 18:23

hey- at a buck each, that aint a bad score actually. actually, now that i think of it....whats wrong with them?? lol.

nice find. where did you get them at a buck each?

Security Flaw- Master Lock 1547DCM

Security Flaw- Master Lock 1547DCM

Who is online