Researchers can make a key based on the sound made when it goes into a lock

Researchers have recently demonstrated a method of creating a 3D printed copy of a key with the design of the key obtained by listening to the sounds made when the key is slipped into a lock. The system doesn't require a high-end microphone. The sounds can be recorded using a smartphone or smart doorbell if it's close enough to the lock.

As odd as this sounds, security researchers say they have proven the series of audible, metallic clicks made as a key slides into a lock can be deciphered by signal processing software. The clicks reveal the exact shape of the sequence of ridges on the key shaft. Once the scientists know this, a working copy of it can be 3D printed.

The system is known as SpiKey, and focuses on the metallic clicks as key ridges hit the locks pins. The team says the clicks are critical to the inference analysis, which is the time between them that allows the SpiKey software to compute the inter-Ridge distances and what locksmiths call the "biting depth" of those ridges. The latter is basically how deeply they cut into the key shaft or were they plateau out.

One way to ruin the analysis is by inserting the key into the lock at a non-constant speed. However, the software is able to compensate for small speed variations. The system outputs the three most likely key designs that will fit the lock used in the audio file that reduces the potential options from 330,000 keys to only three.

The researchers say that one of the three keys printed will unlock the door in question. The upside of this research is that it sounds as if you slide your key into your door lock at an inconsistent speed, you might foil the technology.