Method of achieving effective protection of car interior outfit, in particular a car radio, against stealing

The present invention relates to a method for preventing unauthorized use of a device, in particular a car radio.

It is known to equip the car radio with an anti-theft code. For this purpose, in the memory belonging to the car radio preferably a programmable read-only permanent memory (EEPROM) for the first start or restart after interruption of the car radio power supply, the code must be entered directly in the car radio. This can be done either with the entry keys or via an external code card. The processor assembly integrated with the car radio compares the stored secret code with the entered code and, with compliance, transfers the car radio for unrestricted use.

It is disadvantageous that the secret code on the car radio can be read in a relatively easy way. If the code is known through unauthorized reading, the car sound system can also be activated by unauthorized users.

The essence of the method of preventing the unauthorized use of the device according to the invention, in which, in order to activate the device, the code assigned to this device is entered directly into the device is that the digital data of the generated control information is generated from the code in the irreversible encryption circuit and then compared in a comparator digital data of the generated control information with digital data of the control information stored in the device and, depending on the result of the comparison of both digital data, the device is allowed or not allowed to be used.

Preferably, the asymmetric encryption method is used for encryption.

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Preferably, the RSA (Rivest-Shamir-Adleman) encryption method is used as the asymmetric encryption method.

Preferably, the code-code is determined by the secret key circuit in a secure location for each device.

Preferably, the explicit public key data for the code and the control information digital data are stored in the device.

Preferably, the code control code algorithm digital data and control information digital data are stored in the device.

Preferably, the serial number or part of the device serial number is used as control information.

An advantage of the solution according to the invention, in which the coding is determined by means of an irreversible encryption method from control information assigned to the device, and the anti-theft code itself is not placed in the device, it is not possible to use the anti-theft device.

The subject of the invention will be explained in more detail in the embodiments shown in the drawing, in which Fig. 1 shows the device encryption scheme, Fig. 2 - the device encryption commissioning scheme, Fig. 3 - the device encryption scheme according to the second embodiment, and Figs. 4 and 5 show schemes for starting an encrypted device according to the second embodiment.

Control information 12 is inserted into the irreversible encryption circuit 10, which is processed in the secret key circuit 14, so that the code 16 is created. The control number 12 can, for example, be the serial number of the protected device, i.e. radio car. From this serial number or from part of the serial number, for example, by freely selecting individual items of the serial number, in a secure environment in the production of car radio using secret key 14 a code is created 16. Code 16 is placed on the car radio at the first release or at its desired onward transfer. This can take place, for example, in the form of written information about the code or in the form of a code card which has the stored code 16.

The car radio itself contains a processor assembly in which control information 12 is placed as invariant information and an open key 18 of the asymmetric encryption method used in the encryption circuit 10. Preferably the RSA (Rivest-Shamir-Adleman) method is used for asymmetric encryption.

The car radio 20 shown in FIG. 2, therefore, apart from the public key 18 and control information 12 does not contain the code 16, which is needed to start or restart the car radio 20. For the authorized start or restart of the car radio 20, the authorized user enters the code 16 into of the car radio processor 20. This may occur, for example, by entering the code 16 in writing on the keys or by entering a code card. The encryption circuit 10 generates digital data of the generated control information 12 'from the entered code 16 and public key 18. The digital data of the generated control information 12 'is compared with the stored unchanged digital data of the control information 12 in comparator 22. If the comparison in the computer 22 shows a match between the digital data of the control information 12 and the digital data of the generated control information 12 ', the car radio 20 is transferred for unrestricted use by the user 24.

It is evident that in the case of car theft 20 there is indeed everyone tothe available explicit key 18 of the asymmetric encryption method used in the encryption circuit 10 and control information is also available to everyone, for example, the serial number, but code 16 is not available to determine the generated control information 12 '. Also, code 16 cannot be determined from the explicit key 18 of the asymmetric encryption method used in the encryption circuit 10.

It can be seen immediately that without knowing the code 16 it is not possible to start or restart the car radio 20.

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Since the cost for the irreversible asymmetric encryption method described in Figures 1 and 2 for specific groups of security devices cannot be compared with the achievable benefit, a simplified irreversible encryption method will be described in Figures 3 and 4.

In a manner analogous to FIG. 1, control information, e.g., the car radio serial number, is applied to another encryption circuit 10 '. Using the algorithm of the generating circuit 26, code 16 is determined from the control information. Code 16 is in turn attached to the car radio either in writing or in the form of a code card.

Car radio 20 is restarted or restarted, as shown in Figure 4, by entering code 16 into car radio 20. Encryption circuit 10 'shows code 16 to control circuit algorithm 28 and control information 12. Control circuit 28 checks code 16 in this respect, is it related to control information 12. If the control circuit 28 determines that the code 16 belongs to the car radio containing the control information 12, the user 24 the car radio 20 is allowed unrestricted use.

The irreversible encryption method explained in Figs. 3 and 4 is also characterized in that neither the car radio 20 itself contains the code 16 nor the algorithm of the code generating circuit 26. Only control information 12 and control circuit algorithm 28 are included, which also does not allow direct access to code 16 when unauthorized reading. Only with costly analysis of control circuit algorithm 28 can we deduce the algorithm of circuit 26 generating code word 16. Thus, also in this simplified irreversible encryption method, anti-theft protection is obtained for the car radio or other devices worth protecting.

Depending on the need to secure devices, you can choose between the more expensive asymmetric encryption method according to Figures 1 and 2 or the simpler pseudo-asymmetrical encryption method according to Figures 3 and 4.

Figure 5 shows the activation of the device coded according to the second embodiment in which the code 16 and the control circuit algorithm 28 are fed to the encryption circuit 10 ', which generates the digital data of the generated control information 12' from them. The control circuit algorithm 28 is located along with the control information 12 on the car radio 20. In the comparator 22, the digital data of the generated control information 12 'is compared with the digital data of the control information 12 on the car radio 20 and, with compatibility, unrestricted use by the user 24 of the car radio 20 is allowed.

The embodiments described above explain the creation and use of an anti-theft code for a car radio. In principle, however, this method can be used for all devices worth protecting.

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UP Department of Publications. Circulation of 50 copies

Price PLN 2.00