Alright, I need help with a very unique problem I've got. Does anyone here know a lot about locks or feel like learning a lot about locks in order to help me? Yes, I am picking a lock, but it's only my lock and my hand was forced by curiosity. Here's the situation:

I live in an apartment with 3 other people in individual rooms. We all have keys to the front door (identical) and a key for our room (individual). Obviously, my key opens my door perfectly, and no one else's key works in my door. However, my roommate figured out that our front door keys ALL work on my door with some jiggling and finagling, but no one else's doors can be opened this way.

Yes, we're creepy like that...one-upping and gaining power over each other is a little game we like to play.

So, this made me really curious, and also gave me an idea. There are 5 pins in the lock, and each pin has 7 possible positions to open it. All the pins are, of course, independent of each other. My key is completely different from the front door key, but i refined the jiggling and discovered that all I have to do is push the front door key all the way in, apply a bit of rotational pressure (like i was picking the lock) and pull it out very carefully until SOMETHING lines up just right, and it opens very easily.

So I figure that my front door key might be a combination of the MASTER key cut and my OWN door key cut, only with one of the pins different. It seems to me that this should narrow down the possibilities for the master key a lot. I have a lot of pieces of information here, but I just don't know how to go about putting them together to figure out the cut of the master key.

THIS IS A PUZZLE I HAVE TO FIGURE OUT.
Does anyone with lock picking or smithing experience or knowledge of locks or good math/logic theory have any idea how I can figure this out? It is fascinating to me. Also I already spent the money on a bunch of key blanks and some files, so I'm in it to win it.

bump key

And to make it a more basic logic puzzle:

Cut depths (0 - no cut, 7 = deepest cut) as best as I can gauge them without calipers:
My key: 22321
Front door key: 15240

The cylinder spins freely when the front door key is backed out one pin:

x22321
15240x

I don't know what keys are perfectly lined up and which got "picked" when i put pressure on the lock and pulled the key out a bit.

All I can think of when reading this is Fallout 3.

It sounds interesting but I'm way too lazy to solve it

I'm no master locksmith, but I have played at picking (and read the MIT Lock picking guide, which I recommend as a good starting doc) so I have some minimal knowledge.

The most common trick in picking consumer locks to put tension on the pins, raise each individual pin above its cut depth, then release it and try to get the edge of the pin at the cut to get caught on the edge of the rotating cylinder. (my description is lacking, it's been a while since I've read or talked about lock picking)


In your case, I don't think that we are looking at a master key cut, just a coincidence of pin cuts and cheap consumer lock design.

If you start by fully inserting the front door key, the pins will be in the following positions:

15240

And after removing at little, as you said, they should be:

X1524

If we look at the movement of the pins between these two states, all but one of the pins will either be in the correct position or have an opportunity to catch on the cylinder:

12345 Pin#
-----
22321 Target
15240 Start
X1524 Final (backed out 1)
DUDCD Change (Down, Up, and Correct depth)

Pin 1: starts above the target depth 2, so when the key is backed out, it can catch.

Pin 2: is the trouble pin, it starts low, and gets pushed up above the target, so there is no chance to catch. However, the final pin position is only slightly off (1 vs 2), and there will be a big "ramp" between the 1 cut and the 5 cut, so it's possible between wiggling and cheap lock design that this pin might end up in the correct position.

Pin 3: Again, starts above target depth of 3, so when backed out, can catch.

Pin 4: Final pin depth matches target depth.

Pin 5: Starting pin depth is above target pin depth, then the final position drops, another chance to catch.


So yeah, that's my guess at what's going on. I'm in no way certain, but it makes scene to me this way.

[Edit] Also, go change your locks. [/Edit]

[Edit2] and Bob goes and changes the Front door key depths, still, nothing really changes.[/Edit2]

Call this guy.

That sounds pretty good...basically, it just so happens that our front door key is an almost perfect lock pick for most of the pins in my door.

By applying the torque and moving the key, sounds like your front door key is just acting like a rake and it's setting the pins properly. Your key may be different from it, but the high/lows are aligned such that you can set the pins like a rake in the right order to turn the lock. The other's likely don't have the same high/low order necessary to set the pins.

What he said.

When I used to have to cut keys for the house I worked at in college, the maintenance department had a little tool that told us the depth of the cut.

Yeah, I saw that while i was researching today...I wish I had a bunch of locksmithing tools. That would be an awesome thing to just be prepared to do at all times.

I cut a lot of keys for a couple of years and could almost tell what the "code" was just by looking at a key, but that was just for one specific kind of key. They didn't teach us anything like how to pick locks, but I got to see of one of our maintenance guys pick some locks. Unfortunately, you have to be a locksmith to legally have lock picking kits.

I use to cut keys, install hanldes and that sort. I know how the lock works but I never tried picking one before. I bet I could do it

In a perfect world, depths range from 0 to 7 (or 8 total positions) in a 5 pin lock (I.E. a 5 pin tumbler) would have 32,768 possible keys. However, due to mechanical deficiencies the number can be whittled down exponentially. This can be seen on a standard combination padlock; when entering the combination you can usually be 1-2 numbers off and the lock will still open. With jiggling, keys with notches not off by more than 1 or 2 degrees of depth should work fine. In addition, combinations tend to refrain from repetition (I.E. straight cuts will be avoided, eliminating a few more keys).

For pure lockpicking, two devices can be used to simulate a key, since as long as tension is applied to a certain part in the lock (I don't recall its exact name), the pins won't click back, and you can one by one set each pin into place.

Better yet, call this guy: