Decoding smart keys (I) “Keyless entry” is also safe

Among the many trendy electronic devices in cars, the smart key system is very eye-catching. The keyless entry technology brings excellent convenience, and the one-touch start brings a full sense of technology. The mere change from turning the key to pressing the button is enough to make many bosses spend a lot more money to buy some models that are even only equipped with the top configuration. Smart key system.

However, manufacturers have different definitions of smart keys and the technologies they use. What is considered a smart key system? Is the smart key system safe? Let’s first analyze the “keyless entry” part of the smart key system.

From traditional keys to smart keys

Regardless of the era, car keys are used to open car doors and start engines. As cars are of high value and have certain risks in use, keys are particularly important. In the early days, car keys were just a piece of metal plate. Turning the key opened the door and turned the key to start the engine. It was not technologically advanced. Later, some manufacturers integrated identification chips into the keys, and the car could only be started after dual identification of the key and the chip.

Traditional mechanical key

Later, with the advent of remote control keys, the door locks can be opened or closed by pressing a button from a distance. The remote control is a wireless signal source with the same frequency band as the vehicle. The car door can be opened or closed by issuing a command. We can compare the command to a sentence and the frequency band to a language. It is like the remote control saying "Open Sesame" to the vehicle in Mandarin, and then the vehicle opens the door. However, the vehicle remote control also takes into account the function of the key. The commands for different models are different, and the languages ​​representing the frequency bands for different brands are also different. When other car owners send the Cantonese command "Little Rabbit, open the door obediently" from their remote controls, it naturally cannot match and will not affect our car.

The world-famous folding remote control key

At present, many models are equipped with intelligent keyless entry systems, which allow you to unlock the car and start the engine without taking out the key. The smart key using RFID (Radio Frequency Identification) technology has a verification action when opening the door. When the vehicle is locked, it will continuously send out signals. When the smart key appears within the signal range, there will be a response, completing the verification behavior.

It's like the car shouts "天王盖地虎" every few seconds, and when the key hears it, it replies "宝塔镇河妖", ok, the number is matched, and you don't need to take out the key, just touch the sensor or button on the door handle to unlock. Vice versa, when you leave the car, the car automatically locks and closes the windows (some models do not have the leaving lock function, or require additional settings, so ask clearly when purchasing).

Even with smart keys, you still have traditional keys just in case

Many people may wonder, while technology increases convenience, what about security? Next, let's take a look at the security aspect.

In a vehicle without an anti-theft system, it is very easy for bad guys to drive away your car. Just like on TV, the more violent ones will smash the car window, destroy the ignition lock cylinder, take out a few wires, connect them randomly, and with the roar of the engine, the car no longer belongs to you. The more technological ones will use a series of tools to get all the locks in a few minutes.

Various lock picking tools

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The seemingly convenient remote control also brings convenience to thieves. Early fixed-code remote controls could only send out a code that could not be called a password. With the development of technology, thieves also have tools that can monitor signals. When your remote control shouts "Open Sesame" to your car, others can certainly hear it. When you are not around, the "Open Sesame" that has been recorded long ago is played back, and the car is at the mercy of others.

This is the new signal interception tool for 2009. With the development of technology, the 2011 model should have been launched.

Of course, this simple problem was not difficult for the engineers, so they used a rolling password when designing the remote control, that is, multiple passwords were set on the remote control and changed one at a time, and there was also a corresponding password in the vehicle receiving system. The first time the door was unlocked, it was "Open Sesame", and the second time it became "Open Watermelon", and then "Crab" and "Green Tea" could open the door, which made the previous monitoring equipment ineffective, and the security was naturally improved.

More advanced code interception tools can analyze the signal characteristics of different models

So the thief, who was angry and embarrassed, came up with a ruthless trick. Since I can't monitor your signal, I will make your signal unable to reach. When you parked your car in the parking space and waved your hand to lock the door with the remote control, you didn't find that your car was not locked. The reason is that when your remote control said "Youtiao close the door" in English to your car, the evil thief was shouting "Hee shua shua hee shua shua" and "betray my love" in various languages ​​with a signal jammer. So your car couldn't hear your "Youtiao close the door" clearly, so the door couldn't be closed. Moreover, as long as you have time and technology, it is not difficult to decipher the rolling code.

The box in the middle with three antennas is a signal jammer, which works on the same principle as the cell phone signal blocker in the exam room.

The way the keyless entry system locks the door is completely opposite to the remote control locking method. After turning on the leave locking function (provided that this function is available), when you leave the car with the car key, even if you do not issue a lock command, the car will be locked decisively after it cannot sense your presence, leaving no chance for anyone. As long as no one sneaks into your car during this period, it is basically safe. Although there is no lack of violent means, which thief is willing to choose a difficult vehicle to challenge his skills?

Key verification process topology diagram

In addition, most smart keys use key encryption technology. Unlike rolling codes, key encryption can improve the encryption level and save time for matching codes under the same amount of information. To give a simple example, we can use the key of "number of letter positions minus 1" to convert "zhimakaimen" into "yghlzjzhldm", a code that is not easy to crack. So when the smart key sends the "Ren-o-zmj1- yghlzjzhldm" command to the vehicle, the vehicle will know the information "Ren user requests to open the door - use the key of zmj1 to decrypt yghlzjzhldm". Of course, this is just an example, and the actual encoding and decoding process is very complicated. The collaborative work of rolling codes and keys has indeed greatly increased the difficulty of cracking and ensured security.

summary:

The keyless entry system provides full convenience while ensuring security. In recent years, the remote control keys of models launched on the market also have a key encryption mechanism, which greatly improves security. In the next article, we will introduce the startup part of the smart key system, understand the startup methods and security used by different models, as well as the additional functions and common problems of the smart key system.