Despite, Hack a Day seeming to be fairly lock heavy lately, we’ve yet to cover a major story from The Last HOPE. At the conference, [Jon King] talked about vulnerabilities in Medeco locks and presented his Medecoder tool. Medeco is really what makes this story interesting; unlike the EU, the US has very few high security lock manufacturers. You pretty much have to use Medeco and it’s found in many government agencies.
The Medeco locks have a vertical row of six pins arranged like most pin tumbler locks. Unlike your average lock, the rotation of the pins is important. When the key is placed in the lock, it not only moves the pins to the correct height, it also rotates them to the correct orientation. A sidebar blocks the cylinder unless the pins are rotated properly. Each pin has three possible orientations. They’re biaxial as well, which means the pin’s offset point allows for three more possible positions.
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[Barry Wels] is well known for his lockpicking talks, but this year he wanted to talk about how he copies high security keys. If a key blank is available, you could make a copy just by viewing the original. High security keys generally have profiles with more side cuts, which means you can guess at how deep a specific pin is by observing how many cuts it crosses. He also showed that you could imprint your arm with the key and use that as a guide. If a blank isn’t available, you could fill a similar key with solder and file that down.
[Barry] showed two different kits for casting keys. The first used soft clay in a clam shell to make an imprint of the original key. The form is then filled with a low melting point alloy (probably Wood’s metal) to create the new key. A second style uses a metal form and two part silicone to create the mold. This method works for most high security keys, but will not work on keys with active elements like sliders or magnets.
Finally, [Barry] talked about his favorite method: impressioning. Unlike picking a lock, when you’re done impressioning you have a funtional key. You start with key blank and file off the top layer. Place the blank in the lock and turn it till it jams. Then, you rock the key up and down. Observing the key under light you’ll see a small mark where each pin is. File a bit where the marks appear and repeat the process. You can’t use too much force or you might break the blank. This also works on dimple keys and as this video shows, laser cut keys. [Barry] highly recommends the impressioning book by [Oliver Diederichsen].
[photo: Rija 2.0]