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Comment by nordsieck | Hacker News Reader

> This seems to work on only the most basic of locks, and doesn't seem to address "Security Pins" or false pins (pins if you move, will seize the keyway), which will cause false sets, clicks, partial keyway turns, etc.

I don't see why either of those are relevant.

A key in normal operation won't interact with false pins, and security pins (I assume you're talking about spools/mushrooms) act like normal pins to a key.

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You would get a different sound from the different types of security pins, but even then - not that many and as you say, as its the legit key being recorded - security pins won't do anything than act like a normal pin in operation.

At least have an excuse for leaving the house with the radio blaring out now - security.

> You would get a different sound from the different types of security pins

I'm not sure that's true...it may be true, but it hasn't been looked into. Also 99% of security pins are in the driver pins which aren't the actual pins that are making the clicking sound against the ridges. Since there is a set of pins (key pins) between the ridges and the security pins that could also "dull" the difference security pins change the sound.

In the same vein, though, great locks can also use different springs for each set of pins which also may effect the sound.

If I had a know security pin lock at hand, I'd check it out as have a few contact microphones that are perfect to delve into something like this. Certainly with spectrogram and zoom in after doing high quality recording and soon see what sticks out. Of course would really need a lock in which you have each type of security pin and a normal pin and change that one pin and compare several unlocking. I'd be supprised that there isn't some distinguishing aspect due to shape changes in the pin altering how it responds to vibration. Yes the springs will have some influence, a small scratch in the pin barrel would have a small nuanced effect that with with right measuring, would show up. I'll put it on my winter project list, more so as it may open up the possibility of not even needing a working key and just inducing some sympathetic harmonic with the pin types to induce resonance that can be measured. Could be a fun winter this year.

Agreed. These features are only relevant to picking, not to inserting the actual key.

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