Posts Tagged ‘details’

Electronic lock decoders

Monday, February 15th, 2010

A lot of people asked my opinion about the “Electronic Key Impressioner” that has been in the news lately. The device is not for sale yet and the only thing people have seen so far is a computer model of a device. Technical details are not out yet (as far as I know). This being a news item triggered a lot of people who are now curious if a device like this could really work, and if so, what is the technique behind it.

The automatic key impressioner reminded me on something I saw at a trade-show a couple of years ago. At the stand was a person with a some sort of ‘lock probe’ that could electronically read out the combination on some car locks. This lock probe was connected to a laptop, and after inserting the lock probe in and out of the lock a couple of times, the code of the lock was on the display of the laptop.

lock probe

Curious on how this technique worked, I spend some time talking with the developer of the system. As we all know, most car locks are wafer locks. These wafers all have the same outer dimensions and the only thing that differentiates (for example) a ‘cut one’ from a ‘cut four’ is the position of the hole in the wafer. To make it a little more clear for people who are not into locks, I took wafers one, two, three and four from a car lock and stacked them on top of each other. You can clearly see a ‘stairway’ pattern if you stack them in incrementing order.

stacked car lock wafers

The lock probe I saw at the show used electric current to determine the position of the opening in the wafer. The idea is to put some low voltage on the body of the lock and ‘look for it’ with the contacts in the isolated tip of the lock probe. A high cut wafer will only make contact with the higher contact points in the tip, while a low cut wafer will give a reading on more contact points as the tip slides trough it. And there were a number of different probes for various lock models (variations in the spacing and position of the contact points on the tip of the key). The theory behind this may all look easy and straight forward, but it took them quite some effort to write a decent piece of software to convert the data into a key-code. The developer told me errors could be introduced if users insert the probe too quickly, and sometimes locks ‘in the field’ were so dirty/greased up that contact with the wafers was not reliable.


lock probe

Of course I can only guess, but I imagine the “Electronic Key Impressioner” works on the same principle. I can’t wait to see the device in real life and be able to test it under some real world conditions. As I can imagine there is a range of wafer locks this technique does not work on. And I wonder if it can compete with some of the more sophisticated mechanical car lock decoders that are out on the market for many years now …