Car alarm with dialogue scan protection

Dialogue scan protection

— protection that works 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.

Dialogue systems are somewhat more expensive than dynamic systems, but they are significantly superior in terms of reliability and resistance to hacking; in fact, with the current level of technology, it is impossible to crack such a code using a scanner. Firstly, for this, the attacker must intercept 3 data packets (request, riddle, guess). Secondly, in its pure form, this data is useless — with the next connection request, the system will send another riddle and require a different answer. Thirdly, the encryption algorithm is unique for each central block, and it is almost impossible to “extract” it from the scanned signal: the data in such a signal is encrypted using the so-called hash functions, and breaking this cipher without a decryption key, even on the most powerful computers, would take decades. The decryption key itself is also embedded in the alarm and is not available without physical access to the device.