New Mul-T-Lock: Flex-Fit

[ARF-GEF]

Today I met a fantastic, intriguing lock today: Mul-t-lock Flexfit of the Interactive + family
It is a lock which has a set of keys working at all times (white labelled keys) 2 programming keys (red for banning and green for allowing) and a set of blue keys which can be reversibly allowed and banned whenever you wish so.


The different keys coming with the lock, colours and tags will be explained later on

Quite fascinating, considering how usual 3-in-1 locks are usually a 1 way street. It's a long description, I tried to make it understandable, but bear with it, it's truly an amazing system!
It's not too easy to explain, it took me like 10 minutes to fully get it after disassembly.



You can ID it from the L on the front, the dimples will be important later on

Here is how it works in principle:
The last interactive pin has a 1 level master wafer.
It is essentially has 2 positions: Position "A" when it's stacked in the last set of pins: thus it allows both keyset white (The always opening one) and also keyset Blue (the optional one) to work. As you may have guessed by now the difference between the 2 sets is that the last depth (tip of the key) is 1 deeper with the blue one.

The master wafer has an alternative place: it can slide to the side to a specially made place Position "B". Think of it like a storage place for the wafer. When it's there, the Blue keyset's last depth is too deep, no wafer to bridge the difference and thus it stops working.
Keys White are all functioning naturally. (As do the programming keys, Red and Green).

How does the master wafer change it's place?
let's start when the Blue set is allowed.
You enter with the red key, it has a higher bitting, it pushes out the wafer from the plug. The plug has a specially shaped side in one quarter, (the housing is standard) so the wafer can actually slide to the "side" (doing a route of 90°) and arrive at the Position "B", the storage place.
How come it stays there?
There is a special pin at the site. A semi interactive pin (similar but not exactly like the other interactive pins in the lock) where the internal pin can be pushed a bit though the outer pin. When the internal pin meets a "hole" it happily occupies the place. However when it meets no place (so there is no special biting at the side for it to go into) it's pushed through it's outer wafer slightly protruding at the other side. When it's protruding at the other side it doesn't allow the master wafer to "lodge" itself at Position "B" the storage place. When the key has a biting at the side the internal pin is in the hole at the key and thus not pushed through the outer pin and so the washer has a place to stay. In that case the blue keys are unusable.

So the red keys allow the wafer to move from the stack to the "storage place" and disabling the blue keys and the green keys do the opposite.
It can be repeated as many times as you like.






I really think this is a fantastically clever solution. It is probably not as long lived as a normal lock, but it seems to me like a good concept.
It's only moderately more expensive than the normal interactive plus (like 20$ more per side).

If you have any questions feel free to ask
I hope I got it right lol

[huxleypig]

Wow, this is a very cool system Arf. It reminds me of locks I have read about in the past that allow one time changing of the bitting but this is reversible and very nice indeed.

I suppose having the master wafer makes it just that little bit easier to pick?

[ARF-GEF]

Yes, the master wafer will make it a bit easier to pick. But I think you can easily mess it up so that the once allowed blue keys stop working. So that would be an indication of a picking.
Which is a cool thing IMO.

What I'm currently thinking of is I believe you can hack the system by milling a dimple to the side of a blue key.

Mostly one way rekeying works by sth breaking off from the top of a pin and having pushed then to a little hole at the side of the plug.

[GWiens2001]

Am wondering how it moves the master wafer back in place, allowing the blue key to work again. This is a very creative lock.

Gordon

[xeo]

Very interesting stuff. I'm wondering what happens if you pick it. Who knows what you've just activated? Did you simulate the red key? If so will the next key that enters become banned?

[GWiens2001]

Very interesting stuff. I'm wondering what happens if you pick it. Who knows what you've just activated? Did you simulate the red key? If so will the next key that enters become banned?

Good questions. ARF- you gotta pick them enough times to answer the questions for us! Inquiring minds want to know!

Gordon

[ARF-GEF]

Hhahahaha, I would piss myself in joy if I could pick an interactive just once
Anyhow I'm quite convinced picking it without constant pressure on the side pin will likely result in locking out the blue key if you turn the plug to the right at least 270°or left at least 90°.

[l0ckcr4ck3r]

Very interesting Lock and Great Write up!!

[Oldfast]

Yes, VERY interesting.... and gracefully explained. Thank you!

[Mcof]

My question would be the physical difference between the red and white keys. Also, weather the side pin is compressible.

I'm not sure how accurate this is to the lock, but the function is identical.

Note that the spring pin is stronger than the last driver but weaker than the side pin's. Not ideal, but easy to make into blocks.

But I think you can easily mess it up so that the once allowed blue keys stop working. So that would be an indication of a picking.

Assuming the type is known it should be easy to choose the location of the master wafer post-pick. To enable the blue key, side key pin needs to be kept high when passing the 90° CCW position. To disable it, the last pin needs to be kept high when passing the 90° CW position. The trick would be establishing the original position either during the pick or at the first transition.

[ARF-GEF]

The diff between red and white key is 2 depths at the last place. I don't have the lock here, it wasn't mine unfortuantely, but IIRC white has deeper.

Theside pin's inside part is pretty much like a smaller shorter version of the normal driver pins in the multlock interactives. The inner pin is spring biased and can be presed inside. When it's pressed inside the outer pin it slightly protrudes at the other side.
Does that answer your question?

On your drawing I can't follow why the driver pins is chanigng places from the side to the last pin and back.
Also here is no driver pin on the side pin, just that little thing on the picture (plus optionally the master wafer). It only meets thediver pin of the last pin so they are the same driver pin. That also means that they have teh same spring
But those small things aside I think you got it really well in the drawing, nice job making them
And thanks for posting them here.

Assuming the type is known it should be easy to choose the location of the master wafer post-pick. To enable the blue key, side key pin needs to be kept high when passing the 90° CCW position. To disable it, the last pin needs to be kept high when passing the 90° CW position. The trick would be establishing the original position either during the pick or at the first transition.

Yes I think with care, some skill and the necessary expertise you can spoof it, but as I see it paicking is already quite a feat in itself, and the cahnces of soemone picking it in real life and then knwoing about the trick in it and also following though the feat of controlling the location of the master pin in a stressful real world picking on a door is not quite a common danger, at least not something that I would anticipate.
Of course if you are so highly endangered that such highly skilled expert is a reasonable threat then naturally you shouldn't really realy on this one line of defence.
As I see it IRL you can easily have an accidnet during picking if it' such a small thing as controlling the place of the wafer even if you are skilled. But I guess it so stronyl depends on the person of the picker
Despite that I think it's a very good point what you raised

[Mcof]

This should be more accurate then.



If so then the last pin is less secure than I assumed (however it's done) as is feeling and manipulating the master wafer.

The most significant vulnerability would probably be privilege-escalation from either the blue or white keys. Even if the control pin is random that's only 5 options, some of which might be eliminated by impossibly-high bitting, ironically making the blue key slightly more vulnerable.

[ARF-GEF]

What I'm currently thinking of is I believe you can hack the system by milling a dimple to the side of a blue key.

I agree with you
Though that is also an expert attack. Requiring skill, knowledge, (possibly access to blanks) and key cutting machine.
I don't think escalation attack will be too common IRL, but I also think it's possible.

AS for the drawing it seems correct now at the first sight