Tutorial: The Ordered Combination Lock

Blip · 2014-04-15 12:24:00

Combination locks are pretty secure.. but what if you want them to be even more secure? What if you want to present what seems to be a small, thee or four bit, easy-to-guess lock, but really has more solutions than the robber knows? Then it's time to build your first ordered combination lock.

The basic idea of an ordered combination lock is using electronics to store data on whether one button was powered before another. Essentially, if button 1 was pressed, but button 2 wasn't pressed, power from button 1 would flow into a piece of electronics designed to store that powered state, regardless of whether power from button 1 gets cut off later. This stored "bit" is, in turn, hooked up to a voltage triggered or voltage triggered inverted switch, just as a button would bein a regular combination lock.

Luckily, there's a nice, compact piece of electronics that does just what we need. Here's a unit that, once supplied power, stays powered forever (unless broken by tools):

These bit storage units will be at the core of the ordered combination lock - they can store data over time, which is necessary for our ordering process. Usually, I'll set it up so that power is required to never pass to them, but alternatively, it can be set up that power has to be passed to them. Here's a quick, three bit example, which I'll then explain:

The center button obviously has to be pressed, as its hooked up the the master power line just like it would be in a regular combination lock. However, it's also hooked up to two bit storage units which, if powered, prevent the master power from flowing. Thus, both of the outer buttons have to be pressed before the center button - otherwise, even if power is cut leading to the bit storage units by pressing the outer buttons, the bit storage units themselves stay activated, and still prevent the master power from flowing.
The master power is supplied by another bit storage unit, hooked up to the two outer buttons. This one needs to be activated for the power to be able to get through the lock and to whatever traps it's hooked up to. Here, the rightmost button has to be pressed first, as otherwise no power would ever reach the bit storage unit. Thus, the button order is 3,1,2.

How useful are these locks? Well, here's a 5-bit example, using the same electronics as above, with the two extra buttons only stopping power flow if pressed:

Now, a regular 5 bit lock would have 2^5, or 32 possible combinations, which could eventually be guessed by pure chance. However, an ordered five-bit lock has far more solutions:
5 single button possibilities.
5*4 two button possibilities.
5*4*3 three button possibilities.
5*4*3*2 four button possibilities.
and 5*4*3*2*1 five button possibilities.
Thus, the total number of ways for a combination to be entered into an ordered 5-bit combination lock is:
5+(5*4)+(5*4*3)+(5*4*3*2)+(5*4*3*2*1) = 325 possible combinations.
That's 10 times more possibilities than a non-ordered 5-bit lock! Of course, the ordered lock takes up more space, but if you do have enough room, it's definitely worth building to keep your house that much more secure.

JoyOfTrapping · 2014-04-15 14:05:41

I must be in the slipstream of the TCD collective consciousness, because I was thinking this morning about combination locks, and if it would be possible to create permutation locks.. You sir, have done it. Awesome job, just awesome.

Cylence · 2014-04-15 15:29:27

My problem with combo locks has always been the size.
Do you have a recommended format for the smallest effective ordered combo lock?
If it gets down small enough, I wouldn't mind adding it to the arsenal.

mala · 2014-04-15 16:01:55

great post blip, i hate combo locks but this work is amazing

MMaster · 2014-04-15 16:20:49

Wow! You've done it on much smaller scale than I did when I started with the game. Mine took almost whole house

Great post!

Kimenzar · 2014-04-15 16:25:58

This combolock has a much better Space to Bruteforceratio than usual combolocks. I still think it takes to much space, to be really safe in highlvl houses =/ ( remind this is the really easy version)

GotABigTrap · 2014-04-15 21:27:03

how can you tell what the combination is or how do you set it?

TheNinja · 2014-04-16 12:40:19

It smells like someone is gonna put this to use

booper · 2014-04-16 15:44:56

Cylence wrote:

My problem with combo locks has always been the size.
Do you have a recommended format for the smallest effective ordered combo lock?
If it gets down small enough, I wouldn't mind adding it to the arsenal.

its not an ordered combo lock, but magic dance locks are pretty small. to add one bit, it requires 1 wired wall and 1 button. this is very space effective, IMO.

this is an example from an older post: http://castledraft.com/editor/qGO0xL

Cylence · 2014-04-16 15:58:33

booper wrote:

its not an ordered combo lock, but magic dance locks are pretty small. to add one bit, it requires 1 wired wall and 1 button. this is very space effective, IMO.
this is an example from an older post: http://castledraft.com/editor/qGO0xL

Hi booper, thanks for the tip. However, I already know magic dances are effective and scalable (build however small or big you want). My arsenal is filled with compact leaps of faith linked and layered across magic dances, some shown some hidden, and some fake. I was asking specifically about combo locks since I've always had an issue with their space.

So Blip, can it get any smaller?

Edit: Grammar Police and Spelling Forces Unit

Last edited by Cylence (2014-04-16 15:59:23)

GotABigTrap · 2014-04-16 18:40:03

My question is, is it easy to change the buttons and their order?

Blip · 2014-04-16 18:59:50

GotABigTrap wrote:

My question is, is it easy to change the buttons and their order?

It's not actually that hard. The combination is set by pairs of buttons that have to be hit - i.e. you set which buttons comes first for every set of two buttons that have to be pressed in the combination. To set which button comes first in a pair, one button (let's call it A) has to be connected to a bit storage unit, with the other button (B) connected to a Voltage Triggered Inverted Switch along the wire connecting A to the bit storage unit. The bit storage unit is then attached to your main power line just like a regular button in a combination lock, following these rules:
If you want A to be pressed before B, attach the bit storage unit with a Voltage Triggered Switch.
If you want B to be pressed before A, attach the bit storage unit with a Voltage Triggered Inverted Switch.

Cylence wrote:

So Blip, can it get any smaller?

The big size constraint are the bit storage units; those are the smallest possible bit storage units in the game, and they take up five tiles each. For every possible pair of pressed buttons, you need one, so if you want a lock where 6 buttons have to be pressed, you need 15 individual bit storage units, plus all the wiring to route every button to the proper one. So unless somebody comes up with a way to compare the orders of multiple buttons at once, without having a bit storage unit for every pair, I don' think this lock'll get much smaller.

Nakula · 2014-04-24 12:24:01

i wish i was better at electronics. can you just give an example of the 3 button ordered combo, but a different order? maybe if i see another example ill be able to make my own order.

GotABigTrap · 2014-04-28 18:32:35

http://castledraft.com/editor/jO6Ndh

Here is an example that I've been playing with. In this example, two buttons must be pressed (last two); however, you must press the last button before the middle. In this design, if you press the middle first, it cannot be solved by sawing the middle. Secondly, if you press the first button, it cannot be sawed as we store the charge in a memory cell. Its probably the simplest example, but I think blips version was a bit more scalable for size.

possibilities are something like listed below. Maybe i'm missing some but not sure. That is like 3 X stronger than a typical 3 bit lock, but it does take up a lot more space. On the other hand, similar can be done for 4-bits to achieve a much better results. The nice thing about 3 bit locks is people are more likely to try it.

3+(3*2)+(3*2*1)=15

1
2
3
1,2
2,1
1,3
3,1
2,3
3,2
3,1,2
3,2,1
2,1,3
2,3,1
1,2,3
1,3,2

On the other hand, similar can be done for 4-bits to achieve a much better results. Although, its tougher in a 4 bit example to completely protect from saw attacks. However, permutations would be more like

4+(4*3)+(4*3*2)+(4*3*2*1)=64

It would be twice as good as a 5-bit lock and offer some protection against saw attacks

http://castledraft.com/editor/aLGnGu

Actually, if the robber presses a button out of order,sawwing does no good because the memory power will continue to break the circuit for the unpowered cell that you want to enable.

Last edited by GotABigTrap (2014-04-28 20:50:36)

The Castle Doctrine Forums

#1 2014-04-15 12:24:00

Tutorial: The Ordered Combination Lock

#2 2014-04-15 14:05:41

Re: Tutorial: The Ordered Combination Lock

#3 2014-04-15 15:29:27

Re: Tutorial: The Ordered Combination Lock

#4 2014-04-15 16:01:55

Re: Tutorial: The Ordered Combination Lock

#5 2014-04-15 16:20:49

Re: Tutorial: The Ordered Combination Lock

#6 2014-04-15 16:25:58

Re: Tutorial: The Ordered Combination Lock

#7 2014-04-15 21:27:03

Re: Tutorial: The Ordered Combination Lock

#8 2014-04-16 12:40:19

Re: Tutorial: The Ordered Combination Lock

#9 2014-04-16 15:44:56

Re: Tutorial: The Ordered Combination Lock

#10 2014-04-16 15:58:33

Re: Tutorial: The Ordered Combination Lock

#11 2014-04-16 18:40:03

Re: Tutorial: The Ordered Combination Lock

#12 2014-04-16 18:59:50

Re: Tutorial: The Ordered Combination Lock

#13 2014-04-24 12:24:01

Re: Tutorial: The Ordered Combination Lock

#14 2014-04-28 18:32:35

Re: Tutorial: The Ordered Combination Lock

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