Smart Keys - Security Requirements

Security Requirements

It is important that the vehicle can't be started when the user and therefore the smart key is outside the vehicle. This is especially important at petrol stations where the user is very close to the vehicle. The internal LF field is allowed to overshoot by a maximum of 10 cm to help minimise this risk. Maximum overshoot is usually found on the side windows where there is very little attenuation of the signal.

A second scenario exists under the name relay station attack (RSA). The RSA is based on the idea of reducing the long physical distance between the car and the regular car owner's SmartKey. Two relay stations will be needed for this: The first relay station is located nearby the car and the second is close to the SmartKey. So on first view, the Keyless Entry / Go ECU and the SmartKey could communicate together. A third person at the car could pull the door handle and the door would open. However, in every Keyless Entry / Go system provisions exist to avoid a successful two-way communication via RSA. Some of the most known are:

• measuring Group delay time to detect illegal high values
• measuring Third-order intercept point to detect illegal Intermodulation products
• measuring Field strength of the Electric field
• measuring response time of 125 kHz LC circuit
• using a more complex Modulation (i.e. Quadrature amplitude modulation) which can't be demodulated and modulated by a simple relay station

Furthermore Keyless Entry / Go communicates with other ECUs. Depending on the electric car architecture, there are the following systems which can be enabled or disabled:

• ESCL Electric Steering Column Lock
• EIS Electronic Ignition Switch
• Central door locking system
• Immobiliser
• Engine Control Unit (Motor management system)
• BCU Body control unit