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Relay theft has increasingly become one of the preferred modus operandi among car thieves. In this kind of theft, criminals use relay technology to amplify the RFID (radio-frequency identification) signal being transmitted from your car’s key fob inside the house to bring it closer to your car, allowing them to unlock it and steal it in a matter of minutes. This has compelled car owners to leverage whatever is available to them to stop the relay attacks. While there are several gadgets on the market to prevent this, many car owners use the hack of wrapping the key fob with aluminum foil to stop the RFID signal from being broadcast.
These relay attacks are possible because key fobs of many modern cars are constantly broadcasting RFID signals to enable the car’s keyless features. As a result, car thieves no longer need to force their way into a car or hotwire it. While some car makers have switched to digital keys, allowing you to store your car keys on your Android phone or iPhone, relay theft remains a big problem. Even though the aluminum foil hack may seem jank, there is legitimate science behind it, and covering the key fob with foil can stop the signal and help prevent your car from being stolen. However, there are some caveats.
Using aluminum foil as an electromagnetic shield
Relay thefts rely on being able to receive the signal being emitted by your car key fob, which is where aluminum foil can help. The foil acts as an electromagnetic shield by creating something called a Faraday cage. When the radio waves emitted by your fob hit the foil, some of the waves are reflected or refracted inside the makeshift aluminum housing. The rest of the waves, on the other hand, interact with the aluminum metal in the foil. This interaction causes the aluminum electrons to move around and rearrange themselves to create a counter-force, which cancels out the radio waves, resulting in a tiny amount of harmless heat.
For this DIY Faraday cage to work effectively, it needs to cover the key fob and prevent the radio signals from leaking. For best results, you’ll need to wrap the key fob in multiple layers of aluminum foil; two to three layers are typically sufficient. Keep the wrapping tight, wrinkle-free, avoid tears or gaps, and test it out. This isn’t exactly convenient, since you can’t reuse the same foil every day and you need to be careful how you cover it every time. It’s also susceptible to wear and tear, as a foil isn’t the strongest material, making it most useful in a pinch.
Fortunately, you can easily find cheap RFID blocking pouches on Amazon and other places, which would be significantly better as a safety solution to stop key fob relay attacks for everyday use. This Hoiny Faraday Key Fob Protector is a well-rated option that’s typically sold for $5 and comes with two pouches.
