OK, picture the scene:

I walk down the corridore to my office, open the door... and the handle 
snaps off in my hand.

Yes, you heard me correctly. The handle on the door of my office fell off.

Here's the rub: My door never used to shut properly. The latch didn't 
drop into the slot in the door frame, so you could actually open the 
door without turning the handle.

But they fixed that on Tuesday. So now you actually need to turn the 
handle or the door won't open. (I mean, you turn the handle 
instinctively anyway. But now it's mandatory.) The net result is that, 
thanks to the builders fixing my door, I am now locked out of my office.

Stop and think about that for a moment: I'm locked out of my office. I 
have nowhere to sit. No PC to use. Can't get at any of my paperwork, 
tools or spare parts. I'm homeless.

So I wandered into the tearoom. At was at this point I realised I can't 
actually have a cup of tea either - my cup is... in my office. (As is my 
coat, although technically I'm unlikely to have need of that today.)

Everybody else seemed to think this state of affairs was both utterly 
unbelievable and extremely amusing. I was less amused. (!!)

Anyway, by pure fluke, it turns out there is in fact a solution. I have 
a key that opens the locked server room door. In the process of doing 
this, I discovered that if you turn the key the wrong way, instead of 
locking the door, it lifts the latch. And apparently my key is a "master 
key" that opens several other doors as well. (Doesn't that mean all the 
locks are identical??)

Once I figured out that the lock on *my* door rotates in reverse 
direction [because the door opens the opposite way - WTF?], I was able 
to get back inside. I wasn't going to bother with a cup of tea, but I 
felt I needed it!

And now I've drunk the tea, a thought occurs to me: I am now sitting 
inside my office, with a door that nobody except me can open. (Because 
only I and two managers have any actual door keys.) So... basically 
nobody can come into my office to pester me. I'm locked in, and nobody 
can bother me! :-D :-D

Let the surfing begin!!!

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

On Fri, 20 Jun 2008 10:47:34 +0100, Invisible <voi### [at] devnull> wrote:

>I am now sitting 
>inside my office, with a door that nobody except me can open.

So you are not operating "an open door policy" today? :)
-- 

Regards
     Stephen

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> And apparently my key is a "master 
> key" that opens several other doors as well. (Doesn't that mean all the 
> locks are identical??)

  No. Why would you think that?

-- 
                                                          - Warp

Post a reply to this message

>> And apparently my key is a "master 
>> key" that opens several other doors as well. (Doesn't that mean all the 
>> locks are identical??)
> 
>   No. Why would you think that?

Because any given key only opens locks of the exact same shape?

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

Stephen wrote:

> So you are not operating "an open door policy" today? :)

Oh God, that surely desurves a rimshot! ;-)

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

On Fri, 20 Jun 2008 11:31:44 +0100, Invisible <voi### [at] devnull> wrote:

>Stephen wrote:
>
>> So you are not operating "an open door policy" today? :)
>
>Oh God, that surely desurves a rimshot! ;-)

<g>
-- 

Regards
     Stephen

Post a reply to this message

On Fri, 20 Jun 2008 11:31:23 +0100, Invisible <voi### [at] devnull> wrote:

>>> And apparently my key is a "master 
>>> key" that opens several other doors as well. (Doesn't that mean all the 
>>> locks are identical??)
>> 
>>   No. Why would you think that?
>
>Because any given key only opens locks of the exact same shape?

http://en.wikipedia.org/wiki/Key_(lock)
-- 

Regards
     Stephen

Post a reply to this message

>>   No. Why would you think that?
>
> Because any given key only opens locks of the exact same shape?

Locks can be designed to be opened by two different keys (usually a unique 
key and a master key common to several locks).

Post a reply to this message

scott wrote:

> Locks can be designed to be opened by two different keys (usually a 
> unique key and a master key common to several locks).

Really? Hmm... sounds physically implausible to me, but OK.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

On Fri, 20 Jun 2008 11:46:07 +0100, Invisible <voi### [at] devnull> wrote:

>scott wrote:
>
>> Locks can be designed to be opened by two different keys (usually a 
>> unique key and a master key common to several locks).
>
>Really? Hmm... sounds physically implausible to me, but OK.

That is because you don't know how a lock and key work. They are very
simple physical devices.
-- 

Regards
     Stephen

Post a reply to this message

>> Really? Hmm... sounds physically implausible to me, but OK.
> 
> That is because you don't know how a lock and key work. They are very
> simple physical devices.

The shape of the key aligns a series of pins. By design, exactly one 
shape of key does this. It's difficult to see how you'd make two 
unrelated shapes both have this property.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> The shape of the key aligns a series of pins. By design, exactly one 
> shape of key does this. It's difficult to see how you'd make two 
> unrelated shapes both have this property.

  The simplest lock type is the pin lock: the shape of the key raises each
pin a different amount. Each pin is cut in two parts. If the pin is raised
the correct amount, it will free the pin (as the cut will coincide with the
edge of the lock cylinder). If all the pins are raised the correct amount,
the entire lock will be freed and can be turned.

  In pin locks designed for master keys some of the pins are cut in three
parts instead of two. This means that two differently-shaped keys can open
the lock. When all the locks designed for a given master key have the same
secondary cuts, all of them can be opened with the master key. An individual
such lock can also be opened with the individual key assigned to that lock
(but can't be opened with any other key, except the master key, of course).

  Thus a series of locks with a master keys have all the same pin cut
assignment, plus some of the pins have a second cut, for the lock-specific
key.

  (Of course pin locks are quickly falling out of use, at least in Europe,
because they are so easy to lockpick. Other, more secure lock types are
usually used, but the master key idea is basically the same.)

-- 
                                                          - Warp

Post a reply to this message

On Fri, 20 Jun 2008 12:00:33 +0100, Invisible <voi### [at] devnull> wrote:

>>> Really? Hmm... sounds physically implausible to me, but OK.
>> 
>> That is because you don't know how a lock and key work. They are very
>> simple physical devices.
>
>The shape of the key aligns a series of pins. By design, exactly one 
>shape of key does this. It's difficult to see how you'd make two 
>unrelated shapes both have this property.

Think of a house key, a Yale. The zig zag shape fits into a mask of a
similar shape allowing the key to turn. As you say.
But if on the key one of the high points is reduced then the key will
still turn, as the key will still fit through the mask. With me so
far? Once through the mask the zig zags have to engage a mechanism to
turn the lock. So if you flattened the key to the lowest point it
would turn but not engage the lock. A master key has the relevant zig
zags to engage the lock but not enough to be blocked by the various
masks on different locks.
This is reduced to being too simple.
-- 

Regards
     Stephen

Post a reply to this message

Warp wrote:

>   In pin locks designed for master keys some of the pins are cut in three
> parts instead of two. This means that two differently-shaped keys can open
> the lock.

I see...

Actually, I wonder. They call them "pins", but just how strong are they? 
Couldn't you open the lock just by breaking all the pins?

>   (Of course pin locks are quickly falling out of use, at least in Europe,
> because they are so easy to lockpick. Other, more secure lock types are
> usually used, but the master key idea is basically the same.)

Yeah, they all involve the shape of the key moving the internal 
components of the lock around...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> Actually, I wonder. They call them "pins", but just how strong are they? 
> Couldn't you open the lock just by breaking all the pins?

  Depends on the quality and width of the pins. There are, in fact, locks
(even on the main doors of houses at some places) which can be broken by
simply turning then with enough force. A friend of mine who has lived in
Vancouver says that most locks there were of that type. They were completely
insecure. You could open a door by simply turning the knob with enough
force.

  More high-quality pin locks cannot be broken so easily, but they are
still so easy to lockpick that it's better to use a safer design (for
example a disc tumbler lock, which is common here, and which is extremely
hard to lockpick, and while not impossible, requires very sophisticated
tools).

-- 
                                                          - Warp

Post a reply to this message

>> Actually, I wonder. They call them "pins", but just how strong are they? 
>> Couldn't you open the lock just by breaking all the pins?
> 
>   Depends on the quality and width of the pins. There are, in fact, locks
> (even on the main doors of houses at some places) which can be broken by
> simply turning then with enough force.

Oh, that's cute.

>   More high-quality pin locks cannot be broken so easily, but they are
> still so easy to lockpick that it's better to use a safer design (for
> example a disc tumbler lock, which is common here, and which is extremely
> hard to lockpick, and while not impossible, requires very sophisticated
> tools).

Yeah, well, devise an unpickable lock and somebody will just rip the 
door off its hinges, or break in through a window or something. ;-) 
Weakest point and all that... All you really need is for the lock not to 
be the weakest part of the system.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

scott wrote:
> Locks can be designed to be opened by two different keys (usually a 
> unique key and a master key common to several locks).

We have cool locks on the doors of our houses, designed especially for 
builders. Basically, all the locks can be opened with the master key, 
until the first time you use the lock-specific key that the builder 
gives to the new homeowner.  So, the first time you unlock your own 
door, you lock the builder's master key out. I have only the vaguest 
idea of how they accomplish that.

-- 
Darren New / San Diego, CA, USA (PST)
  Helpful housekeeping hints:
   Check your feather pillows for holes
    before putting them in the washing machine.

Post a reply to this message

And lo on Fri, 20 Jun 2008 16:39:56 +0100, Darren New <dne### [at] sanrrcom>  
did spake, saying:

> scott wrote:
>> Locks can be designed to be opened by two different keys (usually a  
>> unique key and a master key common to several locks).
>
> We have cool locks on the doors of our houses, designed especially for  
> builders. Basically, all the locks can be opened with the master key,  
> until the first time you use the lock-specific key that the builder  
> gives to the new homeowner.  So, the first time you unlock your own  
> door, you lock the builder's master key out. I have only the vaguest  
> idea of how they accomplish that.

They use little ball-bearings between the pins, when the builders use  
their key they shear at the top of the bearings and the bearings stay in  
the plug. When you use your key you raise the pins so the shear line is at  
the bottom of the bearings and when you turn they fall into holes set in  
the plug and are thus removed.

-- 
Phil Cook

--
I once tried to be apathetic, but I just couldn't be bothered
http://flipc.blogspot.com

Post a reply to this message

Phil Cook wrote:
> They use little ball-bearings between the pins, when the builders use 

Well. Now I know. Thanks! :-)

-- 
Darren New / San Diego, CA, USA (PST)
  Helpful housekeeping hints:
   Check your feather pillows for holes
    before putting them in the washing machine.

Post a reply to this message

Invisible a écrit :
> Yeah, well, devise an unpickable lock and somebody will just rip the 
> door off its hinges, or break in through a window or something. ;-) 
> Weakest point and all that... All you really need is for the lock not to 
> be the weakest part of the system.
> 

And do not lose your keys :-)

It's all nice and well to have an unbreakable door and lock until you 
have to destroy your own wall to go into your own house because the keys 
were lost somehow...

-- 
Vincent

Post a reply to this message

> It's all nice and well to have an unbreakable door and lock until you 
> have to destroy your own wall to go into your own house because the keys 
> were lost somehow...

I almost never have this problem. ;-)

My mum has a habit of losing her keys all the time. But then, she just 
slings them wherever she happens to be when she stumbles in through the 
door. And then she wonders why she can't remember where they are. MY 
keys are always in one of exactly two places: In my pocket, or next to 
my computer.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

Vincent Le Chevalier <gal### [at] libertyallsurfspamfr> wrote:
> It's all nice and well to have an unbreakable door and lock until you 
> have to destroy your own wall to go into your own house because the keys 
> were lost somehow...

  If you are the only person owning keys to your house, then the next
step is to contact a legalized locksmith. They have their means to open
doors without breaking too much property. (Usually they can lockpick the
door open with their advanced tools, or if the lock is too secure for
that, they can remove the lock by force, in which case you only have to
pay for a new lock.)

-- 
                                                          - Warp

Post a reply to this message

And lo on Mon, 23 Jun 2008 13:19:07 +0100, Vincent Le Chevalier  
<gal### [at] libertyALLsurfSPAMfr> did spake, saying:

> Invisible a écrit :
>> Yeah, well, devise an unpickable lock and somebody will just rip the  
>> door off its hinges, or break in through a window or something. ;-)  
>> Weakest point and all that... All you really need is for the lock not  
>> to be the weakest part of the system.
>>
>
> And do not lose your keys :-)
>
> It's all nice and well to have an unbreakable door and lock until you  
> have to destroy your own wall to go into your own house because the keys  
> were lost somehow...

I think I'd try a window first ;-)

-- 
Phil Cook

--
I once tried to be apathetic, but I just couldn't be bothered
http://flipc.blogspot.com

Post a reply to this message

Invisible wrote:
> keys are always in one of exactly two places: In my pocket, or next to 
> my computer.

I once spent 2 or 3 hours looking for my keys, because they were in the 
wrong pocket of the trousers hanging on the hook. I checked my pocket! 
They're not there!

-- 
Darren New / San Diego, CA, USA (PST)
  Helpful housekeeping hints:
   Check your feather pillows for holes
    before putting them in the washing machine.

Post a reply to this message

Invisible wrote:
> scott wrote:
> 
>> Locks can be designed to be opened by two different keys (usually a 
>> unique key and a master key common to several locks).
> 
> Really? Hmm... sounds physically implausible to me, but OK.
> 
The keys in my hospital have at least three levels.
I can open my door. There is a master for the floor and there is one 
that opens all doors (and possibly even a level in between). I think you 
can also have more than one master per lock. Then if more than one 
department is on one floor, each department can have a master key and 
the cleaners have one for the floor. Also if the department is split on 
two floors...
And they are all mechanical. The master keys have one extra groove, I 
don't know about the general master.

Post a reply to this message

andrel wrote:
> And they are all mechanical. The master keys have one extra groove, I 
> don't know about the general master.

For that matter, there are cool things you can do with cryptography and 
math that let you have similar relationships with passwords. Stuff like 
"this file can be decrypted by any three of the seven officers of the 
company, or by unanimous application of the keys of the department heads 
of the company. Oh, and we can invalidate any key without invalidating 
the others."

-- 
Darren New / San Diego, CA, USA (PST)
  Helpful housekeeping hints:
   Check your feather pillows for holes
    before putting them in the washing machine.

Post a reply to this message

Darren New wrote:
> andrel wrote:
>> And they are all mechanical. The master keys have one extra groove, I 
>> don't know about the general master.
> 
> For that matter, there are cool things you can do with cryptography and 
> math that let you have similar relationships with passwords. Stuff like 
> "this file can be decrypted by any three of the seven officers of the 
> company, or by unanimous application of the keys of the department heads 
> of the company. Oh, and we can invalidate any key without invalidating 
> the others."
> 
I personally think doing it in hardware with nuts and bolts is more 
impressive, but that may be just me.

Post a reply to this message

andrel <a_l### [at] hotmailcom> wrote:
> I personally think doing it in hardware with nuts and bolts is more 
> impressive, but that may be just me.

  I suppose it's simply a question of cleverly allocating combinations
of pin assignments to locks and keys. I can imagine at least one simple
way of achieving a hierarchy of master keys with pin locks:

  In all locks, all pins have a cut for the highest-order master key,
as well as the secondary cut for the lock-specific key.

  The locks are divided into groups of locks (eg. on a per department
basis). All the locks in one group have the exact same secondary cut
for the first pin, but this secondary cut is different in different groups.
This way a master key for a specific group of locks uses the group-specific
setting for the first pin, and for the rest of the pins it uses the setting
for the highest-order master key. This way it can open all the locks in its
own group, but it can't open the locks of the other groups (the first pin
being different stops it).

  (If there are too many groups, using just one pin to differentiate between
them might not be enough, but in that case more pins can be used for this
purpose. The amount of combinations increases exponentially.)

  If each group should be further divided into smaller sub-groups, the
same technique can be used with the second pin, the third pin, etc.

  Then there's the reverse problem: All keys, including lock-specific ones,
should open a common lock (eg. the door leading to the entire department).
A lock-specific key should open, naturally, its own lock *and* the common
lock, but it nevertheless must not be a master key which could be used to
open your work pal's office. Obviously master keys should also open these
common locks as well. However, the lock should not be openable by a key
not related to the company at all.

  In other words, the situation is kind of a reversal: The common lock is
a "master lock": It should be openable by a group of keys, but not by any
keys outside that group.

  I have difficult time bending my mind into resolving how exactly it is
done, but I can perfectly imagine there's a simple way. Ingenuous, but simple.

-- 
                                                          - Warp

Post a reply to this message

andrel wrote:
> I personally think doing it in hardware with nuts and bolts is more 
> impressive, but that may be just me.

I definitely agree. I wasn't disparaging. I was simply saying you can 
make it even *more* complex with math. The fact that the program doesnt 
have to enforce the cryptography stuff is what makes *that* impressive 
to me. You can't unscramble the stuff without 3 or 9 keys due to the 
nature of the keys, not the nature of the lock, so to speak. :-)

-- 
Darren New / San Diego, CA, USA (PST)
  Helpful housekeeping hints:
   Check your feather pillows for holes
    before putting them in the washing machine.

Post a reply to this message

Warp wrote:
>   I have difficult time bending my mind into resolving how exactly it is
> done, but I can perfectly imagine there's a simple way. Ingenuous, but simple.

Math professor writes an equation on the board, and says "The proof is 
trivial.  Wait, is it?"  He wanders back to his office, returns in 20 
minutes to the classroom, and says "Yes, indeed, the proof is trivial."

-- 
Darren New / San Diego, CA, USA (PST)
  Helpful housekeeping hints:
   Check your feather pillows for holes
    before putting them in the washing machine.

Post a reply to this message

On Fri, 20 Jun 2008 11:31:23 +0100, Invisible wrote:

>>> And apparently my key is a "master
>>> key" that opens several other doors as well. (Doesn't that mean all
>>> the locks are identical??)
>> 
>>   No. Why would you think that?
> 
> Because any given key only opens locks of the exact same shape?

Go and find a copy of the MIT Guide to Lock Picking.  Seriously.  It 
explains this and you learn a lot about the mechanics of mechanical locks 
from reading it.

Jim

Post a reply to this message

On Fri, 20 Jun 2008 12:00:33 +0100, Invisible wrote:

>  It's difficult to see how you'd make two
> unrelated shapes both have this property.

Two shearing points in the pins.

Jim

Post a reply to this message

Darren New wrote:
> Warp wrote:
>>   I have difficult time bending my mind into resolving how exactly it is
>> done, but I can perfectly imagine there's a simple way. Ingenuous, but
>> simple.
> 
> Math professor writes an equation on the board, and says "The proof is
> trivial.  Wait, is it?"  He wanders back to his office, returns in 20
> minutes to the classroom, and says "Yes, indeed, the proof is trivial."
> 
Old but still gold :-)

John

-- 
I will be brief but not nearly so brief as Salvador Dali, who gave the
world's shortest speech. He said, "I will be so brief I am already
finished," then he sat down.

Post a reply to this message

On Tue, 24 Jun 2008 08:12:00 +0100, Doctor John <doc### [at] gmailcom>
wrote:

>Darren New wrote:
>> Warp wrote:
>>>   I have difficult time bending my mind into resolving how exactly it is
>>> done, but I can perfectly imagine there's a simple way. Ingenuous, but
>>> simple.
>> 
>> Math professor writes an equation on the board, and says "The proof is
>> trivial.  Wait, is it?"  He wanders back to his office, returns in 20
>> minutes to the classroom, and says "Yes, indeed, the proof is trivial."
>> 
>Old but still gold :-)
>
That happened in one of my high school maths classes (true). Now I
think the teacher just went for a fag. (Cigarette)
-- 

Regards
     Stephen

Post a reply to this message

> For that matter, there are cool things you can do with cryptography and 
> math that let you have similar relationships with passwords. Stuff like 
> "this file can be decrypted by any three of the seven officers of the 
> company, or by unanimous application of the keys of the department heads 
> of the company. Oh, and we can invalidate any key without invalidating 
> the others."

Sounds like BluRay encryption to me :-)

Post a reply to this message

>  I suppose it's simply a question of cleverly allocating combinations
> of pin assignments to locks and keys. I can imagine at least one simple
> way of achieving a hierarchy of master keys with pin locks:

Our office keys have the normal jagged key cut for the pins in the lock, but 
then they also have another "key" feature engraved on the side, like a 
series of recesses drilled at certain points.  Maybe some locks only work on 
one set of features, or some on both, I don't know.

Post a reply to this message

Darren New wrote:

> I once spent 2 or 3 hours looking for my keys, because they were in the 
> wrong pocket of the trousers hanging on the hook. I checked my pocket! 
> They're not there!

Yeah, I've done this.

Also, if my pockets are too small to hold all my items, and I know I 
don't need one of them, I leave it behind. I then spend the whole day 
thinking I've lost something because my pockets are not the correct 
weight. o_O

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

Phil Cook a écrit :
> And lo on Mon, 23 Jun 2008 13:19:07 +0100, Vincent Le Chevalier 
> <gal### [at] libertyALLsurfSPAMfr> did spake, saying:
> 
>> Invisible a écrit :
>>> Yeah, well, devise an unpickable lock and somebody will just rip the 
>>> door off its hinges, or break in through a window or something. ;-) 
>>> Weakest point and all that... All you really need is for the lock not 
>>> to be the weakest part of the system.
>>>
>>
>> And do not lose your keys :-)
>>
>> It's all nice and well to have an unbreakable door and lock until you 
>> have to destroy your own wall to go into your own house because the 
>> keys were lost somehow...
> 
> I think I'd try a window first ;-)
> 

I was assuming that the windows were armoured in the same unbreakable 
fashion as the door, of course :-p

-- 
Vincent

Post a reply to this message

Jim Henderson wrote:
> 
> Go and find a copy of the MIT Guide to Lock Picking.  Seriously.  It 
> explains this and you learn a lot about the mechanics of mechanical locks 
> from reading it.
> 
> Jim

Or just simply take one lock apart and check what it has eaten :). 
Preferably a one that has master-key -functionality, then you'll 
understand that also ;).

-- 
Eero "Aero" Ahonen
    http://www.zbxt.net
       aer### [at] removethiszbxtnetinvalid

Post a reply to this message

And lo on Tue, 24 Jun 2008 10:15:12 +0100, Invisible <voi### [at] devnull> did  
spake, saying:

> Darren New wrote:
>
>> I once spent 2 or 3 hours looking for my keys, because they were in the  
>> wrong pocket of the trousers hanging on the hook. I checked my pocket!  
>> They're not there!
>
> Yeah, I've done this.
>
> Also, if my pockets are too small to hold all my items, and I know I  
> don't need one of them, I leave it behind. I then spend the whole day  
> thinking I've lost something because my pockets are not the correct  
> weight. o_O

Heh had this yesterday, parked my car on the drive and got out to open the  
garage door and fell into conversation with my neighbour. Put my hands in  
my pockets and thought "Where are my car keys?". I've been doing the same  
with my camera case it feels weird to go out without it now.

-- 
Phil Cook

--
I once tried to be apathetic, but I just couldn't be bothered
http://flipc.blogspot.com

Post a reply to this message

Jim Henderson <nos### [at] nospamcom> wrote:
> Go and find a copy of the MIT Guide to Lock Picking.  Seriously.  It 
> explains this and you learn a lot about the mechanics of mechanical locks 
> from reading it.

  Every lockpicking guide I have seen talks only about pin locks. Thus
they help understanding how pin locks work, but they don't really help
understanding how other types of lock (such as disc tumbler locks) do.

-- 
                                                          - Warp

Post a reply to this message

On Tue, 24 Jun 2008 08:15:47 -0400, Warp wrote:

> Jim Henderson <nos### [at] nospamcom> wrote:
>> Go and find a copy of the MIT Guide to Lock Picking.  Seriously.  It
>> explains this and you learn a lot about the mechanics of mechanical
>> locks from reading it.
> 
>   Every lockpicking guide I have seen talks only about pin locks. Thus
> they help understanding how pin locks work, but they don't really help
> understanding how other types of lock (such as disc tumbler locks) do.

But for Andy's points, he's dealing with a pin lock, so it would be an 
appropriate reference.

Jim

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On Tue, 24 Jun 2008 13:08:54 +0300, Eero Ahonen wrote:

> Jim Henderson wrote:
>> 
>> Go and find a copy of the MIT Guide to Lock Picking.  Seriously.  It
>> explains this and you learn a lot about the mechanics of mechanical
>> locks from reading it.
>> 
>> Jim
> 
> Or just simply take one lock apart and check what it has eaten :).
> Preferably a one that has master-key -functionality, then you'll
> understand that also ;).

True, taking one apart would teach you a lot as well.

Jim

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Warp wrote:
> andrel <a_l### [at] hotmailcom> wrote:
>> I personally think doing it in hardware with nuts and bolts is more 
>> impressive, but that may be just me.
> 
>   I suppose it's simply a question of cleverly allocating combinations
> of pin assignments to locks and keys. I can imagine at least one simple
> way of achieving a hierarchy of master keys with pin locks:
> 
>   In all locks, all pins have a cut for the highest-order master key,
> as well as the secondary cut for the lock-specific key.
> 
>   The locks are divided into groups of locks (eg. on a per department
> basis). All the locks in one group have the exact same secondary cut
> for the first pin, but this secondary cut is different in different groups.
> This way a master key for a specific group of locks uses the group-specific
> setting for the first pin, and for the rest of the pins it uses the setting
> for the highest-order master key. This way it can open all the locks in its
> own group, but it can't open the locks of the other groups (the first pin
> being different stops it).
> 
>   (If there are too many groups, using just one pin to differentiate between
> them might not be enough, but in that case more pins can be used for this
> purpose. The amount of combinations increases exponentially.)
> 
>   If each group should be further divided into smaller sub-groups, the
> same technique can be used with the second pin, the third pin, etc.
> 
>   Then there's the reverse problem: All keys, including lock-specific ones,
> should open a common lock (eg. the door leading to the entire department).
> A lock-specific key should open, naturally, its own lock *and* the common
> lock, but it nevertheless must not be a master key which could be used to
> open your work pal's office. Obviously master keys should also open these
> common locks as well. However, the lock should not be openable by a key
> not related to the company at all.
> 
>   In other words, the situation is kind of a reversal: The common lock is
> a "master lock": It should be openable by a group of keys, but not by any
> keys outside that group.
> 
>   I have difficult time bending my mind into resolving how exactly it is
> done, but I can perfectly imagine there's a simple way. Ingenuous, but simple.
> 
Our keys are more or less saw shaped, if you know what I mean. The 
master keys have this extra groove. It also has bigger indentations on 
some points. Put another way, if you have 3 or more keys that have the 
same master, all you need is a mechanical workshop to make a master. But 
don't tell anyone, I am not supposed to know.

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scott wrote:
> Sounds like BluRay encryption to me :-)

Yes, except there you need the players to actually enforce the 
encryption and the key invalidation, to a large extent. (How much, I 
don't know for sure, since they kind of conflate a number of different 
operations in one structure.)

But yes, that sort of encryption stuff fascinates me. :-)

-- 
Darren New / San Diego, CA, USA (PST)
  Helpful housekeeping hints:
   Check your feather pillows for holes
    before putting them in the washing machine.

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Jim Henderson wrote:
> True, taking one apart would teach you a lot as well.

Yeah, like not to take apart a lock anywhere near shag carpet if you 
ever expect to put it back together again.

-- 
Darren New / San Diego, CA, USA (PST)
  Helpful housekeeping hints:
   Check your feather pillows for holes
    before putting them in the washing machine.

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Warp wrote:
> understanding how other types of lock (such as disc tumbler locks) do.

I think rather than "pick locks", what you're looking for there is 
"crack safes". :-) That sort of thing teaches you how the rotary-dial 
locks work. Between tumbler locks and rotary-dial locks, it's pretty 
easy to figure out how the variants work (like the ones with dents in 
the keys, or teeth cut on angles, etc.)

-- 
Darren New / San Diego, CA, USA (PST)
  Helpful housekeeping hints:
   Check your feather pillows for holes
    before putting them in the washing machine.

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>> True, taking one apart would teach you a lot as well.
> 
> Yeah, like not to take apart a lock anywhere near shag carpet if you 
> ever expect to put it back together again.

...or just not to expect to put a lock back together, ever?

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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On Tue, 24 Jun 2008 12:58:49 -0700, Darren New <dne### [at] sanrrcom>
wrote:

>Jim Henderson wrote:
>> True, taking one apart would teach you a lot as well.
>
>Yeah, like not to take apart a lock anywhere near shag carpet if you 
>ever expect to put it back together again.

LOL how true :)
You need a wooden floor to hear where those bits bounced to ;)
-- 

Regards
     Stephen

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On Tue, 24 Jun 2008 12:58:49 -0700, Darren New wrote:

> Jim Henderson wrote:
>> True, taking one apart would teach you a lot as well.
> 
> Yeah, like not to take apart a lock anywhere near shag carpet if you
> ever expect to put it back together again.

This is also true. :-)

Jim

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