How A Tin Can Is Able To Protect Your Car From Getting Stolen

It is honestly scary how tech savvy car thieves have become lately. We used to worry about someone smashing a window, but now they can steal a car without even touching the keys. It makes you feel a bit helpless knowing your car could disappear from your own driveway while you sleep. But it turns out that the solution to this sophisticated problem isn't buying an expensive alarm system. You likely have the answer sitting in your recycling bin.

Understanding The Relay Attack

Thief in hoodie trying to unlock car door at night.
Photo Credits: tonodiaz / Envato Elements
Photo Credits: tonodiaz / Envato Elements

To understand why this works, you have to know how the bad guys operate. Your modern car key is constantly sending out a faint radio signal waiting for your car to answer. Thieves use a special device to amplify that signal from inside your house and beam it to your car in the driveway. It tricks your car into thinking the key is right next to the door. Then, they can unlock it and drive away in seconds without ever having to break in.

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The Science Behind This Hack

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A hand holding a car key with a key Fob.
Photo Credits: smile23 / Envato Elements
Photo Credits: smile23 / Envato Elements
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This is where that humble tin can comes into play. Metal is excellent at blocking radio waves. When you put your keys inside a metal container, you are creating something called a Faraday cage. It acts like a shield that stops the signal from leaking out. If the signal cannot get out of the can, then the thieves cannot boost it to your car. It effectively makes your key invisible to the outside world.

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Choosing The Right Container

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A person putting their car keys in a coffee can.
Photo Credits: ManMade DIY
Photo Credits: ManMade DIY
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You do not need anything fancy to make this work. An old coffee tin or a clean soup can works perfectly. Even those little mint tins can work if your keychain is small enough. The most important thing is that it is made of metal and has a lid that fits relatively tight. You want to minimize any gaps where the signal might escape. I just use an old cookie tin I kept from the holidays, and it works great.

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Testing It Yourself

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A man trying to open his car door with his keys in a coffee can.
Photo Credits: ManMade DIY
Photo Credits: ManMade DIY
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You should definitely test this before you trust it completely. Put your keys inside your chosen can and put the lid on. Walk out to your car and try to open the door or press the unlock button on the handle. If the car stays locked, then you know the shield is working. If the door opens, you might need a thicker can or a tighter lid. It gives you real peace of mind to see it fail.

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Making It A Habit

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A coffee can on a small table by the entryway of a house.
Photo Credits: ManMade DIY
Photo Credits: ManMade DIY
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The hardest part is just remembering to do it every day. I keep my tin right on the entryway table where I usually drop my keys. At first it felt a little silly putting my keys in a coffee can like I was hiding a treasure. But after a few days it just became muscle memory. It is a small extra step when I walk in the door that ensures my car will still be there in the morning.

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It is funny to think that, in a world of complex computer crimes, the best defense is a piece of leftover kitchen trash. We often feel like we need to spend money to stay safe but sometimes physics gives us an easy solution. I hope this simple trick helps you sleep a little sounder tonight, knowing your car is safe. It is nice to know you can outsmart a thief with nothing more than an empty can of beans.