2011年11月14日星期一

Obd2 Immobilizer System Overview and Introduction

During 1993 the worldwide increases in automotive theft reached a level which was no longer acceptable for insurance companies. The German insurance companies forced the rapid introduction of a new form of immobilizers security systems. In other regions various forces such as government agencies also started placing more emphasis on vehicle security.
During a short time frame the automotive industry developed various systems to prevent thieves from entering and/or starting the vehicle. The methods chosen vary from country to country depending on consumer preferences. Remote keyless entry for example is preferred in the USA and in France whereas transparent systems are widely spread in the German market. Due to the unique features of RFID and due to the fact that this technology was already existing for industrial applications, most of the automotive industry decided to make use of small batteryless transponders which offer a high level of security at low cost.
Since the beginning of 1995 nearly all models for the European market are equipped with OEM immobilizers. First statistical analysis of insurance companies in Germany confirm the tremendous success of these systems. Thefts of vehicles with electronic immobilizers decreased to about one tenth compared to vehicles without immobilizer. However criminal organizations have the means and the resources to develop high sophisticated equipment to overcome existing systems. Constant improvement of the security architecture is necessary to be one step ahead. This article describes the different security levels of key-based immobilizers and presents the, new crypto-transponder generation which offers the highest level of RFID security.
Key-based immobilizer systems consist of four main components. The core of the system is the transponder, a batteryless device which is available in various form factors and with different functionalities. For operation, the transponder has to be supplied with energy from an external source. The transceiver generates a high frequency magnetic field which is radiated by an antenna coil. The energy activates the transponder and it sends a data stream in form of a modulated RF signal. This signal is demodulated by the transceiver and then passed to the controller for data processing.
Different physical principles for RFID systems have been established on the market. Concerning the transmission of energy, two different systems can be distinguished.
Full Duplex Systems:The energy for the transponder and the data signal generated by the transponder are transmitted at the same time, usually using load modulation.
Half Duplex Systems:The transmission of the energy for the transponder and the data signal from the transponder are transmitted consecutively. The transponder stores energy in a capacitor and as soon as the transmitter is switched off, the energy is used to transmit data.
The different techniques have an impact on system design and reading range respectively reliability in the application, but have no impact on the system security.

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