Some drivers wrap their key fobs in aluminum foil to block radio signals and prevent thieves from “relay attacks”, a method where criminals amplify your fob’s wireless signal to unlock and start your vehicle. While foil can reduce signal strength, it’s not the most reliable or practical long-term solution. Modern alternatives such as signal-blocking pouches, secure storage habits, and proper key fob maintenance offer much stronger protection and are recommended by locksmith professionals.

Understanding the “Foil Trick”

The idea behind wrapping a key fob in foil is simple: Aluminum can block or weaken electromagnetic signals. Since many modern vehicles use keyless entry and push-to-start fobs, which constantly broadcast short-range signals, some drivers wrap their keys in foil at night or in public places to prevent this signal from being hijacked.

But how effective is this method?

Let’s break it down.

What Is a Relay Attack?

Modern push-to-start vehicles use a fob that communicates with the car via encrypted RF signals. In a relay attack:

1. A thief uses a signal-boosting device near your home (often by a wall, window, or front door).

2. This boosts the fob’s signal, even if the fob is inside your house.

3. A second thief near your car receives the boosted signal.

4. The car unlocks and starts because it “thinks” the fob is nearby.

This type of theft is fast, silent, and requires no forced entry.

“Relay attacks are real, but they rely on accessing the constant broadcast signal of your fob. Disabling or blocking that signal is the key to preventing this type of theft.” - KeyMe Locksmiths

Does Wrapping Your Keys in Foil Actually Work?

Foil can reduce signal strength, but it is:

• Inconsistent

• Easy to tear

• Inconvenient for daily use

• Not reliable against stronger relay devices
  

If you wrap a key fob in multiple layers of foil, it may block the signal entirely—but the solution is fragile and impractical.

Bottom line: Foil is better than nothing, but it's not a long-term security strategy.

Better Alternatives to Foil

Here are locksmith-recommended options that provide more reliable protection.

1. Use a Signal-Blocking (Faraday) Pouch or Box

Faraday containers use layers of conductive material to block wireless signals. These are designed specifically for key fob protection.

Benefits:

• Reliable signal blocking

• Durable and convenient

• Available in small sizes for daily carry

“Faraday pouches solve the biggest weaknesses of foil, durability and consistency. They’re a low-cost, high-reliability solution for fob security.” - KeyMe Locksmiths

2. Store Your Keys Away From Entry Points

Most relay attacks happen near:

• Front doors

• Garages

• Windows

• Exterior walls
  

Store your keys centrally in your home, away from exterior surfaces.

This greatly reduces the chance a thief can reach your fob’s signal.

3. Disable Passive Entry (If Your Vehicle Allows It)

Some vehicles let you turn off the key’s constant broadcast signal when not in use.
This prevents relay attacks altogether.

Check your vehicle’s owner manual for:

• “Passive Entry”

• “Smart Key”

• “Keyless Access”

• “Proximity Unlock”

If available, disable it at night for added security.

4. Use a Spare Key Strategy

If you have duplicate fobs:

• Keep one in regular use

• Store the backup in a Faraday box or secure indoor location

• Avoid carrying both fobs together
  

Need a spare fob or key?

KeyMe Locksmiths kiosks and mobile technicians support 38,000+ vehicle key and fob combinations.

Explore automotive key services: https://key.me/vehicle-keys 

Should You Wrap Your Spare Key in Foil?

If you don’t have a Faraday pouch, wrapping a spare key in foil is better than leaving it unprotected, especially if it’s stored near exterior entry points.

Just remember:

• Use multiple foil layers

• Check that the signal is actually blocked

• Replace the wrap regularly to avoid tears
  

But whenever possible, upgrade to a more secure option.

Additional Car Security Tips

• Lock your car manually and check handles

• Park in well-lit areas

• Use a steering wheel lock as a visual deterrent

• Keep valuables out of sight

• Update vehicle firmware when available

FAQs

Is foil good enough for daily use?

Not recommended, foil tears easily and isn’t consistently effective.

Can thieves really start a car without the key?

Yes. With relay attacks, thieves trick the car into thinking the key is close enough to authorize ignition.

Do older cars need protection?

Vehicles without push-to-start systems are less vulnerable to relay attacks but still benefit from good key security practices.

Can a locksmith program a new fob if mine is stolen?

Yes, KeyMe Locksmiths technicians can erase old fob access and program a new one.

Final Thoughts: Foil Helps But Better Tools Exist

Wrapping your car key in foil can reduce your risk of relay attacks, but it’s not a reliable or convenient long-term method.

For strong protection, Faraday pouches, secure storage habits, and professional key services offer far greater peace of mind.

Need a new fob or want to disable a lost one? https://key.me/vehicle-keys
Copy or replace a vehicle key at a KeyMe Locksmiths kiosk: https://key.me/kiosks