A Faraday box for car keys - What is it? How does it work? How much does it cost and do you need one?

Criminals have embraced technology and it’s helping them steal cars.

Many modern cars are equipped with keyless entry/start systems and thieves have figured out they can start these new cars without the vehicle’s actual key fob.

Crooks use portable electronic equipment to amplify or mimic the key fob’s 'Radio Frequency Identification' (RFID) – or signal relays – in order to open the car and start the engine. These are known as relay attacks.

Due to a rise in the number of car thefts in Australia being committed using this method, car owners have been forced to look for more effective car anti-theft devices and technologically advanced methods to prevent the theft of their vehicles.

That’s why a Faraday box, Faraday case (or bag or a Faraday pouch for car keys) is being increasingly used in an attempt to prevent cars being stolen using these key-fob-imitating methods.

It all boils down to needing a car key signal blocker and if you use a Faraday key fob protector it will reduce the chance of your vehicle being taken without your consent.

What is a Faraday box?

In very basic terms, a Faraday box is a receptacle which prevents electro-magnetic signals from reaching whatever is inside that receptacle.

How does it work? What is its purpose?

As mentioned above, a Faraday box (or bag, pouch, or Faraday sleeve) prevents electro-magnetic signals from reaching whatever is kept inside the box. This means the device is unable to transmit or receive any cellular, GPS, Bluetooth and Wi-Fi signals.

These containers can be used to store phones, laptops, tablets, etc in order to prevent them from being accessed remotely by anyone with a proclivity to commit crime, and also protect the items inside from electro-magnetic pulses (EMPs). Don’t know what that is? Just ask your doomsday prepper mate.

In the case of car crime, crooks use a transmitter to impersonate the key fob by relaying the key fob’s signal to the car in order to open and start the vehicle.

Why and how were they invented?

Plenty of great things have come out of England: football (soccer), jellied eels and… scientist Michael Faraday. Never heard of him? Let me enlighten you.

Faraday discovered the principle behind what was to become known as the Faraday Cage in 1836 while messing around with a metal tin. He discovered that if he put an object inside the tin, and put an electric charge on the tin, the voltage did not affect the object inside the tin.

By making this and other discoveries, Faraday altered our idea of electricity and magnetism. Nice one, Mick.

Michael Faraday. Photograph by Maull & Polyblank - Iconographic Collections. (This file comes from the Wellcome Collection, see bottom of article for full attribution)

Why are they used for car keys?

A Faraday cage for car keys (or box, pouch, etc) is used because these containers prevent the key fob’s signals being remotely accessed by thieves and being used to open and start a vehicle that is not theirs.

What are they made of?

A Faraday box/cage/pouch/bag is made from material that is an electrical conductor (including metals such as copper, aluminium, and steel), anything that blocks electromagnetic radiation around the exterior of the receptacle.

In the case of a Faraday box for car keys that might be typically used in a home, it may be lined with a metallic material or mesh, which is designed to prevent any electronic signals from entering or leaving the box.

Do they work?

Yes, Faraday boxes work, effectively blocking all external electromagnetic signals, including RFID signals, from reaching the device(s) contained within the box, so data can’t be remotely accessed. It’s virtually a vehicle immobiliser because thieves are unable to get the car to budge.

Below are a few Faraday receptacles we’ve included here for reference – they’re in no particular order.

Note: Simply because we’ve included these products here does not represent our endorsement of the company, its product or its product’s efficacy.

1. SLNT Faraday RFID Blocking Key Fob Guard

Product description: The Key Fob Guard Faraday bag is “a privacy and security case for your key fob or keyless entry fob – a single sleeve that blocks the wireless connection from your key fob to your car”, according to the official product description. It “Blocks 100 dB+ Blocks Cellular, Wi-Fi, Bluetooth, GPS, RFID, NFC, EMP, and EMF Radiation” and “Blocks 315 MHz frequency used for most North American made cars and 433.92 MHz for European, Japanese, and Asian vehicles”.

Price: $44.95

2. Faraday Box and Two Car Key Bags Fob Anti Theft RFID Security

Product description: This Faraday box “can block various signals such as car key signals, Bluetooth, Wi-Fi, GPS, GSM calls, and NFC, ensuring maximum security for your devices”, according to its retailer.

Price: $38.49

3. The GoDark Vault - Key Fob Faraday Cage

Product description: This vault “Blocks all signals to keyless remote or key fob, 433.92 MHz for European, Japanese, and Asian vehicles, 315 MHz frequency used for most North American made cars, CDMA, GSM, DCS, PHS, 3G, 4G, 5G, LTE, WiFi (2.4–5 GHz), Bluetooth (2.4 GHz) and GPS (1–2 GHz), RFID and NFC in 13.56 MHz”, according to its online description.

Price: $86

How to make a Faraday box

You can create a DIY Faraday box simply by putting your phone in aluminium foil shaped as an envelope, then putting that inside a thick cardboard envelope before taping up the whole thing so it’s sealed off from the outside world. Voilà! Spycraft 101. You could do the same thing using a chip packet and you don’t need the extra aluminium foil.

How to test a Faraday box?

Try calling the phone that’s inside the Faraday box and see what happens. If it rings, you’ve built or bought yourself a dud. If it doesn’t ring, you might just be the smartest person in your suburb.

Note: Image of Michael Faraday from Wikimedia Commons. Title: Michael Faraday. Photograph by Maull & Polyblank. Image has been edited and cropped in both uses here.

This file comes from the Wellcome Collection, a website operated by Wellcome Trust, a global charitable foundation based in the United Kingdom. Refer to Wellcome blog post (archive). This file is licensed under the Creative Commons Attribution 4.0 International license.