Homebrew pick resistant lock

[FarmerFreak]

I felt that this lock was worth re-posting since all the topics disappeared. I have made a few modifications and will give a better explanation of the security weakness it has.





And here is a link to all of it's inner workings.
http://i669.photobucket.com/albums/vv59 ... 25/029.jpg

It has two springs on one side so the pins always stay seated on the opposing side. It also has master pins on the opposite side of certain springs. this is to make the pins in those chambers stop before moving past the keyway. All of this is so the key can enter the lock without a problem.

The modifications that I made: I added 2 anti-impression pins and chambers, and a couple of serrations. I should probably add more serrations, but I felt this was good enough for a demo lock that I still cannot pick.

Anti-impression pins are of my own creation, they aren't in any manufactured lock that I know of. The way they work is such that when they are held at a certain shallow depth and the lock is turned, (the other pins have to be at the correct depths) The anti-impression pins are lifted off of the blank preventing it from marking. This is only possible because there is an angled hole cut in the side of the lock cylinder housing, which allows the pin to move over and be lifted.

I also added the anti-impression and serrated pins to help deter this decoding attack I am about to show you.



If you use a site tool, you may call it a straight pick if you like, you can feel if the split inbetween the pins. And hold down the pins on one side to check the other side. If you find a split this means that that side of the key is a shallow cut and the other side is a deep cut. If you can't find a split in a specific chamber than the key cuts will both be in the center of the keyway.



The serrations and anti-impression pins can make doing this annoying because your tool will catch on the serrations. Though to be perfectly honest this is still a valid method of attack against this lock.

Also someone mention an idea of trying to pick half of the lock, which would allow you to decode it. You wouldn't be able to turn it just click them in place to decode it. And yes on a hand made version of the lock that I have here this is certainly a possibility (though I haven't tried it). But if the plug was made from one solid piece instead of two, I don't think this would be a real threat. I'm sorry I forgot who posted this as I really liked the idea behind the attack.

I hope you enjoyed my custom lock.
Farmerfreak

[mh]

Thanks a lot for re-posting this! As far as I can tell, this time the posts will stay...

[NanoDuke]

How strong is the key? Surely if this were a real lock, you'd use stiffer metal?

[FarmerFreak]

The key is stronger than I originally expected. But yeah I'm not going to try and break it.

My original idea was to make it out of a good piece of pick material. But finding a piece big (thick) enough and the fact that it would be much harder to make. I just grabbed the brass blank of the board and had at it. It has held up since so I haven't worried much about it. But yes I would definitely want to have the key made from steel if the lock were in use.

[NanoDuke]

All valid points there.

I'm just throwing thoughts around. I love problem solving exercises.

Maybe if the keyway was longer (taller?) to give more width (not thickness) to the key. Cause as the prototype stands now, the key will fail quite often. You could make the key out of some carbon fibre composite / alloy, but then it'd be expensive and hard to manufacture.

Argh, but then a taller keyway would make picking easier, especially the decoding problem you mentioned.

I'm new to the game, so forgive me if my ideas/questions seem meaningless. I wasn't around long enough to read everything in the OSL before it got wiped.

Also someone mention an idea of trying to pick half of the lock, which would allow you to decode it. You wouldn't be able to turn it just click them in place to decode it. And yes on a hand made version of the lock that I have here this is certainly a possibility (though I haven't tried it). But if the plug was made from one solid piece instead of two, I don't think this would be a real threat. I'm sorry I forgot who posted this as I really liked the idea behind the attack.

Just to clarify, why do you say that having a single piece plug would prevent decoding?

[FarmerFreak]

As far as making the key out of carbon fiber. I'm not sure it would be a good material for this. Check out this post by Datagram
viewtopic.php?f=4&t=44548
He made a carbon fiber pick, it's cool, but it broke.

Just to clarify, why do you say that having a single piece plug would prevent decoding?

As it is the lock probably has enough slop in it, that you could pick one of the plugs a little bit. The pins in the other plug would mostly be over lifted. So as is you could pick half, when the plug turns a little (very little) you could feel around with your pick on one side (ignoring the other side) and decode the lock.

If the lock was comprised of one plug instead of two halves. Then you would have to pick both sets of pins before the plug could turn a little. But at that point you would be able to pick the lock anyway.

Maybe if the keyway was longer (taller?)

Argh, but then a taller keyway would make picking easier, especially the decoding problem you mentioned.

Correct. But if I could make the plug as a whole taller and leave the keyway small, the decoding problem would disappear. Since the smallest depth pin would still be long enough that the split would never enter the keyway.

Old Corban master key rings/sleeves(whatever they are called) would likely do the trick. You would just key them to the outer sleeve.

as the prototype stands now, the key will fail quite often.

In theory you may very well be correct. But thus far the lock hasn't failed once. The first day I finished it I had to of cycled tested the key at least a hundred times. But yes I'll bet that if I put the key in my pocket and sat on it once it wouldn't work anymore.

I'm new to the game, so forgive me if my ideas/questions seem meaningless. I wasn't around long enough to read everything in the OSL before it got wiped.

Don't worry they aren't bad. You are going to learn a lot more by asking the questions and coming up with ideas. So don't stop.

[NanoDuke]

This thought came to me at 1am this morning. How does this stand against jiggler type pick keys?

[FarmerFreak]

Hmmm....I don't know for sure. I am what you might call a single pin picking fanatic. I don't think it would work because any time you put a pick into the lock you would be over lifting pins (even in the locks resting position several pins are over lifted). Unless the picks shape matched the key shape very closely I myself don't think it would work. But then that would be more of a try key type of attack.

But I honestly don't know. The most I have played with a rake/jiggler type pick, is with a bogota that I made since getting on these forums. Mine may not have been made very well, but it works on cheap locks pretty well. I can only get it to work on a few factory Schlages myself. And this lock is basically two factory Schlage cylinders put together. Except it was keyed specifically such that any pick entering the lock would over lift pins, which basically makes picking negligible.

If I ever found this to be a problem. I have a trick up my sleeve to make it even harder to pick. I could either re-drill the last chamber, or file/sand down the pins in the last chamber. With the intentions of making it so the very last set of pins in the lock will always bind last. muahahaha. But I don't really want to do that, sometimes that's like asking for the lock to fail.

[Arcturus]

Interesting. It's similar to Jacob Rabinow's opposed pin lock. The patent is worth reading, as it incorporates some interesting ideas that might be of use in your design:

http://www.google.com/patents?id=WDM4AAAAEBAJ

http://news.google.com/newspapers?id=5XAQAAAAIBAJ&sjid=Z4sDAAAAIBAJ&pg=6141%2C3356947

Your design takes a more traditional approach, however, in that the bitting surface is on the edge of the key. Rabinow's design puts the bitting surface on the flat side of a wavy shim-like key. In practice, Rabinow's flexible shim key would probably lose its shape after a while. Even if it were made of spring steel, I'm pretty sure the key would get all bent out of shape banging against any other keys inside your pocket. On the other hand, your design would easily adapt itself to a traditional keyway. Although broaching a paracentric profile will be difficult to do in a home workshop.

Since the pins are directly opposed, I am assuming that you'll need some way to prevent the key from being removed while the plug is rotated 180 degrees. Perhaps a ball bearing key retainer? That should prevent the pins on one side from dropping into the opposite side's chambers and causing a lockout.

[FarmerFreak]

Thank you for sharing Arcturus. That patent is virtually identical to what I have done.

Since the pins are directly opposed, I am assuming that you'll need some way to prevent the key from being removed while the plug is rotated 180 degrees. Perhaps a ball bearing key retainer? That should prevent the pins on one side from dropping into the opposite side's chambers and causing a lockout.

On the lock I used, it can't be turned 180 so this isn't a problem. But in actuality it isn't much of a problem anyway. The driver pins are too long on the opposing side to allow the key to come out of the lock at 180 degrees.

[NanoDuke]

Interesting. It's similar to Jacob Rabinow's opposed pin lock. The patent is worth reading, as it incorporates some interesting ideas that might be of use in your design:

http://www.google.com/patents?id=WDM4AAAAEBAJ

http://news.google.com/newspapers?id=5XAQAAAAIBAJ&sjid=Z4sDAAAAIBAJ&pg=6141%2C3356947

That looks like a simple version of a dimple lock, if I'm not mistaken.