Availability of alarm
protection from scanning ; if the characteristics specify the type of such protection, it is also given in this clause.
Scanning is used by attackers to intercept the control signal from the key fob; by forging such a signal, the hijacker can safely open the car. Accordingly, this protection is aimed at preventing such hacks. And its main types nowadays are
dynamic code and
dialog code, here are the features of each of these methods:
— Dynamic code. The general principle of dynamic coding is that each time you press the button to turn on or turn off the alarm, the key fob gives a new, unique signal. Most often, the Keelog algorithm is used for this; it assumes that the signal from the key fob contains data on the serial number of the device, the number of clicks and the secret code that the central unit also “knows” (this code is written at the factory and is unique for each alarm). Based on the serial number, the system performs general identification of the key fob, the click counter confirms that the signal has not been sent before, and the secret code acts as an encryption key. Thus, even if an attacker intercepts and copies the signal from the key fob, this signal will be outdated and, accordingly, useless; and it is impossible to decipher this signal and reproduce the desired version without a secret code.
The main advanta
...ge of systems with dynamic coding is simplicity and, accordingly, low cost. However, this method in itself is less perfect than the dialog code, it provides a lower degree of protection against interception and hacking — with the help of the so-called dynamic code grabber with a jammer, an attacker can still intercept the control code under certain conditions and open the machine. However this procedure is quite complicated and does not give a guarantee; so in general, dynamic code is a good option for inexpensive cars that are not particularly attractive to professional crackers. But for maximum protection, it is still better to use dialogue systems.
— Dialogue code. Protection operating on the principle of “friend or foe” recognition: before giving a control signal, the key fob and the central unit exchange service data, identifying each other and making sure that the signal comes from the rightful owner. This is done in the following way. When you press a button on the key fob, it sends a connection request with data about its serial number. The central unit checks the serial number and, if the result of the check is positive, sends a randomly generated number to the key fob. The keyfob processes this number according to a certain algorithm and sends the result (together with a request for action) to the central unit, which performs calculations according to the same algorithm; if the results agree, the defense gives the go-ahead to execute the command. The algorithm used for calculations is unique in each individual signaling, and so-called hash algorithms are used to encrypt the transmitted data. Due to this, the dialogue code is almost impossible to crack: for this, the attacker must intercept 3 data packets (request, riddle, guess) and decrypt 2 of them, while without knowing the key (embedded in the alarm itself and inaccessible without physical access to the device), such a decryption nowadays is inaccessible even to the most powerful computers.
Dialogue systems are naturally somewhat more expensive than dynamic ones, but this is more than offset by a high degree of security.
