I tried a lifestyle car stealing difficult hand "relay attack" measures with familiar goods.

What is a relay attack?

"Relay attack" means that a weak radio wave that is always emitted by the "smart key" is received and amplified with a special device.In addition, by relaying the amplified radio waves, it is a method of misunderstanding as if there is a key near the car, opening the key and starting the engine to steal the car.This trick is detailed in another article.

In order to prevent this relay attack, it is effective to block the weak radio waves that the smart key always emits, and is generally known as a material that can block radio waves.

Experiment with radio blocking goods

So, this time, I tried to see if the key of the car was wrapped with such material goods to prevent relay attacks.I tried the goods with the ones in the photo below, which are easy to get anywhere.

[Radio blocking goods]

・ Aluminum foil ・ tin can ・ Aluminum steamed PET bottle case ・ Relay attack prevention case

【experimental method】

1.Usually, the distance that the door can unlock with a smart key is measured.

2.Editor A has a smart key in radio -blocking goods, and the editorial staff B can touch the doorknob to check if they can unlock.

3.The editorial staff A steps away from the car one step at a time and strides the distance that cannot be unlocked.

4.Repeated 2 to 3 with each goods.

Usually check the distance that the smart key operates

First, I checked where the smart key operates at which distance the smart key works without using radio blocking goods.Of course, I was able to unlock the car door, of course, at the distance of 0 steps, so only one step, an editorial staff A with a smart key left the car.It is the distance to reach the doorknob.When the editorial staff B touched, the door lock could be unlocked at this distance.

What about next two steps?Then the door lock could not be unlocked.By the way, even if the editorial staff A with a smart key stood in the 0 steps in the back of the curma, the editorial staff B could not unlock the driver's seat door.It seems easier to respond if there is a smart key on the driver's seat.

Tin cans are effective for blocking radio waves

This is a tin can purchased at a 100 yen shop.It is a material similar to cookies and candy cans at home.

Close the lid firmly and start from the distance of 0 steps.What is the effect?What!When the editorial staff B touched the doorknob, they could not unlock.The tin cans used this time did not respond even if the radio wave blocked effect was excellent, even if it was taken to the door knob.The effect of the radio wave is different depending on the material, so the effect cannot be said in general, but this is likely to be a relay attack measure.

In the plastic bottle case, radio waves leak from the gap

This is a plastic bottle case in which an aluminum sheet with a cooling effect is steamed inside.It is said that the case where aluminum material is used inside, such as a bag -shaped portable ashtray case, has a radio blocking effect.I'm worried about the gap because it's a chuck type, but is it really effective?First, start from the distance of 0 steps.After all, the radio wave was leaking from the chuck part, and I was able to unlock it.

If you go down one step, you can still unlock.Since it stopped reacting in two steps without countermeasure goods, 1.Let's go 5 steps.Then I could not unlock.In this plastic bottle case, the gap between the chucks was so good that it was a bit of a concern for relay attacks.

Aluminum foil is effective but troublesome

Next, aluminum foil for cooking.In the plastic bottle case I mentioned earlier, it wasn't very effective, but what about this?

First, start from the distance of 0 steps.What!The smart key wrapped in aluminum foil could not be unlocked.Even if you approach the distance of the doorknob, it does not respond at all.This is quite effective.However, when the smart key was lightly covered, the radio wave seemed to leak, and the effect became weaker, and it was possible to unlock at 0 steps.

Although it is effective, it is a little troublesome to imagine getting off the car every day and wrapping the key in aluminum foil.It is inexpensive and effective, but not practical.

Aluminum foil was reflecting radio waves

It turned out that aluminum foil was effective, and an interesting phenomenon occurred the moment I opened an aluminum foil wrapped in a smart key.The door lock was unlocked with the sound of "Pipit".At this time, the editorial staff B did not touch the doorknob, so the door lock should not be unlocked.

Apparently, I pressed the unlocking button before opening the aluminum foil.But when the aluminum foil was opened, the door lock was unlocked?I wrapped it again in aluminum foil and pressed the unlocking button.

Since the radio waves are cut off, there is no response.After pressing, I opened the aluminum foil for about 2 seconds and was locked again.It seems like the radio waves trapped in the aluminum foil are opened outside as soon as they open and the door lock reacts at a time difference.However, it is impossible, so if you press the unlocking button, the radio wave will be transmitted for a few seconds.

Relay attack prevention pouch

Finally, a big favorite "Relay Attack Prevention Case" appeared.It is a commercial case developed to prevent relay attack, and it is said that materials that block electromagnetically interrupt them are used.Although it is a type that stops with Velcro, it seems that the effect can be expected because the mouth of the case is closed firmly.

First, start from the distance of 0 steps.When I touched the doorknob, the door lock did not respond at all at the distance of the doorknob.Unlike tin cans and aluminum foil, it seems to be portable and easy to use.By the way, if you do not close the case firmly, the effect will be weakened, and if the smart key can be seen, the door lock can be unlocked if the distance is 0 steps.

Put it in a case and store it away from the entrance

In this experiment, it was found that aluminum and tin material, which are said to have the effect of blocking radio waves, may leak the radio waves of the smart key if there is even a gap.Even if it is a zipper -type aluminum steamed plastic bottle case, as well as a goods that claims to prevent relay attack, the door lock can be unlocked if there is a gap.

Conversely, it was confirmed that the radio blocking performance of these materials was quite high if they were firmly sealed with aluminum or tin material.The point is how to seal a smart key with radio blocking material.

In this experiment, the tin cans that combine robustness, radio -blocking, and sealing are the number one.

[Relay attack countermeasure goods comparison table]

* Each item ★ 3 is scored as a perfect score.