Low-Tech Access Control: Master Keying Explained

By Brian Rhodes, Published Jan 09, 2020, 10:03am EST (Info+)

Mechanical keys are one of the most fundamental forms of access control. 'Master Keying' can allow individually different credential keys to segment access, but requires no electricity, no network, and uses regular door locks.

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*** ****** **** **** ** *** widely **********. ** **** ********, ** explain:

  • *** **** ***** ****
  • ******* *** '*****' ** **** ***
  • *** ***** ***** *** ** *********
  • *** ****** *** ******* *** *********
  • ****** **** ** * **** ****
  • ******* ****** *** *****

*******, ***** *******,**** *** * ******** ****.

Basic **** ********

*** ****** ** '*** *******' ***** locks *** *** ******* ***** *** original ******* ***** ** *** *****. Not **** *** **** ****** **** globally, **** *** **** *** **** basic ********.

*** ******** *** ***** ****** * good *********** ** *** *** *** interacts *** ********** ***** * ****:

*** ********* ** ******: *** **** contains ******* (******* ******* * - 7) ******** **** ** ********* *******. A *** ** **** **** ** turn *** **** ** *** '****** combination' ** *** **** ******* *** length ** *** ****.

* ***** *** ******** *** ****** of *** *** **** ** ***** top "***** *****" ***** ******* *** core (*** **** **** *****) *** the ******* (*** ******, ******* ****) of *** ****. ** ******* *** may ** **** ** ***** **** the ****, *** *** ****** *** cuts ** *** ******** ***** *** pins, ********** *** **** **** *******.

Codes ****** ****

**** *** *******, *** *** ********** series ** *** **** **** **** them, *** ******** ********* ** ****.

* ************ *** **** ** **** allows * ********* ** *** * replacement *** ***** ****** *** **** it ***** **** **** * ****. Various ********** ** * **** ****** between **** ******, **** *** ******** depth ** * ***, *** ***** of * ***, ** **** *** width ** * ***, *** *** nomenclature ** * '*** ****' ** fairly **********.

*******, *** ***** ** * *** falls **** ***** ** **** ******** depths, ***** * "*" ***** ********* the *** ** *** *** ** all, *** * "*" *** ******* over *.***" ** ********. ***** *** range ** ****** ** *** ***********, a **** ** ********* ********, *** even *.***" ******** *** ** *** difference ******* * **** ******* *** remaining ******.

**** *** ****** ** **** ** six ****, *** **** ** ********* as * ****** ** ****** **** each ******* ************ *** *** ****** for * ***** *** ********.

*** ******* *** ***** *** * code******, **** **** ****-**-*****:

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** * ****** ***** ******, ***** are ********* ** **** **** **** one ****** *** **** ***** ****. We **** ******* *** **** ******* in *** ********* ********.

Master ****** *******

*********** * ****** *** ** * single *** **** *** **** **** locks. * ******* ****** ****** ****** resembles *** **** *****.

**** **** ***** ****** ** **** correspond ** *****/**** **** **** ****** credentials ********* *** ******:

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******** ** *** ****** *** ******* up:

  • ****** ****:***** *** **** ****** ** ***** who **** **** ****** ** * single ****; ********'* *** *******, ****** cabinets, ***. ***** **** ********* **** only *** ****.
  • ****** (** ***-******) ****:***** *** **** ****** ** ********, that *** **** ** **** * range (*** *** ***) *****. *** example, *** *********** ******** ** **** to **** *** ********** *********** *******, and ** **.
  • ***** ****** ****:*** ***** ****** *** ***** *** doors, ********** ** ***** ***-****** ** patron **** *** **** ** ***. For *******, ******** *************** **** ***** keys ** **** ****** ** *** apartments.

** *** **** ** *** ***** above, *** **** *** **** **** key ***** - ******, ******, *********** - ** ***** **** * ********* bitted ***********, *** **** *** ******* to *** **** "****** ****** ******". Master *** *********** **** ***** ****** like *** ***** ***.

Master **** ********* *** *** **** ****

***** *** ****** ** * **** powerful ***, **** *** ********* ******* controlled *** ******.

** **** *****, ****** **** *** not **** ** ********** **** ***** actually ******, *** **** ********* ***** use ** ******** ***** *******.

Same ******* *** ********* ****

*** ********** ** ******* ***** ** how * ****** ****** ****** *****. Locks ** * ****** ***** ****** are ***** ** **** *** ********* key *** ************.

***** **** *** *** ***********, **** all *** *** **** **** *******. Locks ** ***** ******* ********* ****** be **** ** *** **** ****** Key ******. ** ***** **** ******* in ****** ** ****** **** ****** *******: ********** ************.

Losing ****** **** **** ****

*** ** *** ******* ********** ** a ****** *** ****** ** * high-level ***, **** * ******, ***********, or **** ***** *********** *** ***** lost ** ******. ** **** *******, then ***** **** ** ** ***** for ** *********** ** **** ** being ******, *** *** **** '***' is ** ***** ***** **** **** - *********** ******** ** ***** *** many ********* ** ******* ** ********* and *** *** ******** *****.

**** **** ****** ********** * ****** key ****, *** ******* *** ***** staggering - **** **** ***** ***** a ** ******* ******** **** *** ******* ** **** hundred ******** *******.

**** ********* ***** ******** *** ******* or ******* ****** **** ** *** despite *** ********* ***** *********. ** also ** *** ** *** ******* advantages ** ********** ****** *******, ***** if * ********** ** **** ** stolen, ** *** ** *********** ****** off *** **** ** ** ******* - ** ******* ***** ** ****** required.

Shear ***** **** ****** ****** ********

*** ********* ***** ***** *** * lock ***** **** ** **** *** a ****** '***** ****', ** ***** pin ******* **** ******* ** ** even ********** ******* **** ******.

*******, ******* ** ***** ****** **** of ********* *******, ****** **** ******* use **** **** ** ** ******* different ****** (***** *********). *** ***** below ***** ****, ***** * ****** 'pin' **** ** ******** *********** ** 4 ** * *****, *** ***** more **** *** ********* ***** **** is ******** ****** * *** *******:

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*** ************ ** ******** ***** ***** in * *** ***** *** *********** of ******* ********* **** ******* *** same ****. ** * ****** *** system, *** ***** *** ***** **** a ****** ******** ***** *****. *******, the **** **** *** **** *** tightly **********. *********, *** ***** ******* the *** ** * ****** ***, but **** ****** *** ** **** issued ** '****** ***'.

*** ***** ***** ** ******* **** at *** *******, ***** ********* ** a ****:

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*** *** ***** *****, *** *** inserted *** **** *** ****. **** key *** * ******* **** ********.

*******, * *** ***************** **** **** **** ****, ** would * *** *********, ** *** ***** ********** ***** combination **** ******* * ***** **** up ** **** *** **** ****.

** ***** ******** ***** *****, **** that **** ** ******** *********** ** another *** *********** **** *** **** door. ** **************** ********* ******** ***** line ************ **** *** ******/*********** ****, entire ****** ******* ** ********* ** locks *** ** *****, *** *********** openable **** * ****** ***.

Master ****** *****

*** **** ** ******** * ****** keying ****** ** ******* ******** ** a ***-****** ****** ****** *** ***** thousands **** *** **** **** ********** access.

** *******, **** *** ******* ***** can ** *********** ** ******* **** a ******, *** *** ***** **** are ****** ****** ***** *** **** locksmiths. ******* * **** *** *** in * ****** *** ****** ******** more ***** *** ** ******** **** pins, *** ******* ** *** **** more **** * *** ******* **** for **** **** ** *******.

*** **** ********** ******* ** ******** a ****** ****** ****** ** ********** each ********** *** **** *** **** pinning ****, *******, **** **** ************* and **** ******** ************ **** ** this *** ** **** **** ****** hardware. ********** *********-***** ******** *** ** purchased *** **** **** $***, *** even ******** ******** *** ** **********, although ******* *** **** ***** ** locks/keys *** ** *******.

*******, *** ******* **** ** * master ****** ****** ** *** ********** management ** ****. ** ***** *** the ****** ** ****** ******, ***** time * *** ** ****** ** reclaimed ** **** ** **********. ***** most ***** ******* ******** ***** *****, a ********* ****** ***** ** ***** to *** *** **** ******* ***** knowing *** ***** ***** ***** *** being ****, ** **** **** *** inadvertently *** * ****** ** *********** key *** ****** ***.

****

*******, ***** *******,**** *** * ******** ****.

Comments (19)

Does having multiple shear lines make the lock easier to pick?

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Interesting question.

My opinion is yes, multiple shear lines make a lock easier to pick. To that point, multiple shear lines are easier to 'bump' as well.

But picking a lock, even with multiple shear lines, is more tedious than what movies and TV depicts. It can take hours to pick a 7 pin lock. :(

To make picking/bumping more difficult, lock makers often use 'security pins' with tapered geometry that give a potential picker 'false positives' when picking a lock:

The way the pin is machined 'feels' like it has been picked and may even allow for the core to be slightly turned to the picker's euphoria. But in reality, the pin is still not at a shear line and the lock will stay secure.

Because picking is done mostly by feel and not sight, this is an effective deterrent.

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I picked up a lock pic set and how to book many years ago. First page in the book states "if you can't pick the lock in 3 mins kick the door in"

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I mean, it's true.

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i'm not a big reader, fortunately though:

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But picking a lock, even with multiple shear lines, is more tedious than what movies and TV depicts. It can take hours to pick a 7 pin lock.

Eh, I don't bother with movies and TV. I just watch Lock Picking Lawyer. For example:

Of course, LPL is slightly better at lock picking than most people.

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In fairness to lock picking, the skill needed to pick a lock installed in a door is vastly different than uninstalled in a bench vise.

The amount of torque he can apply is much greater at desktop level with his hand over the lock than if the lock was installed in a door with a handle set or exit device putting tension on the tailpiece.

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To make picking/bumping more difficult, lock makers often use 'security pins' with tapered geometry that give a potential picker 'false positives' when picking a lock:

that's dishonest! we're supposed to be the good guys, right?

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Great Job Brian

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Great article Brian.

I would suggest that key "impressioning" and photography are also viable techniques for compromising many pin tumbler locks.

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"When news breaks describing a mater key loss, the amounts are often staggering - like this story about a US college where the loss was claimed at five hundred thousand dollars."

what do they do with all the replaced cylinders?

sounds like somebody could pick up a multilevel key system on the cheap.

sure there would be the stolen master out there, plus all those people with legit masters and change keys.

but they would get thrown away after the locks changed.

FOR SALE: Used 4 LEVEL Master Key System, 10 Years Old, From 5000+ Miles Away, make an offer!

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In most cases, the lock cores are repinned but not thrown away. The door keys are tossed, but they aren't good for much at that point.

The money is mostly labor to redesign the system, repinning cores, cutting new key blanks, and distributing the new keys.

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took the quiz.

one suggestion: the phrase "commonly not actually made" may be confusing since it's "commonly not actually said" :)

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Thanks. I edited that one/ reworded it to avoid the awkwardness.

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so can an expert locksmith tell a master key just by looking at it, without seeing the lock?

it doesn't sound like it. so nothing, besides the impotent "DO NOT DUPLICATE" command, would prevent a locksmith from unwittingly duping a master?

also, i'm guessing even if a LS was presented with two keys, a master and a patron key, he couldn't tell one is the master of the other, or that they were even related.

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I don't want to say 'it is impossible', but it is unlikely even an expert locksmith could ID a master just by reading a single key. Multiple keys, maybe, but not just one.

With that said, I would not be surprised if there was a savant somewhere who could calculate the probability of a master system's shear lines just by seeing a single key.

That's space cadet stuff, but I'm certain that mathematical tendencies exist.

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More importantly who do I ask to copy a key that states Do Not Duplicate? Asking for a friend who is trying to avoid our HOA $500 penalty for a lost pool key...

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You can try a key-copying kiosk like MinuteKey or Key Me for that.

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