How sound can betray your key and open your lock

Did you know that the sound of your key can tell you a lot? Researchers from the National University of Singapore have discovered how the sound of a key pattern can be analyzed. This can all be done with an app like SpiKey. All you need is a smartphone with a good microphone.

How does it work?

When you insert a key into a lock, it creates a unique rattling sound. The pins in the lock hit the ridges of the key, causing multiple clicking sounds. These clicks contain information about the shape of the key. SpiKey analyzes these sounds and converts them into a digital pattern. This way, you can open a lock without a key by determining the exact shape of the key.

What do you need?

All you need is a smartphone with a microphone. The app SpiKey does the rest. It records the sounds and analyzes them. With just a few clicks, you can already see what a key looks like. No complicated tools, just technology and sound.

So how do you make a key from sound?

Every key has a fixed pattern of cuts, with different depths for each pin in the lock. These depths are standardized by manufacturers. For example, if a pin is 3 deep, it means that the corresponding cut in the key must also have a depth of 3. SpiKey listens to the clicks and calculates the time between the sounds. These time intervals correspond to the distances between the ridges and the depths of the cuts in the key. By combining this with the standard factory values, the app can create a list of possible key patterns.

Suppose a key has six cuts and SpiKey recognizes that the clicks correspond to depths of 2, 4, 3, 7, 5, and 6. The app can use this information to generate a key pattern. A duplicate of the key can then be made with a key machine. The result is a copy that fits perfectly into the original lock.

Get started yourself

Are you inspired to learn more about how to open a lock without a key? Then consider a lockpick set. This allows you to practice and learn how different locks work. It’s a fun and challenging hobby that keeps your skills sharp. We also have a educational guide for beginners where you can learn how locks work.

Sources and more information

The technology behind SpiKey was developed by researchers from the National University of Singapore. Their research “Listen to Your Key: Towards Acoustics-based Physical Key Inference” is a great resource if you want to dive deeper into the technology.