Method for protecting a hands-free access and/or starting system of a vehicle by modifying the speed of signal reception

摘要

Method for improving the security of communication between the electronic key and vehicle to prevent interception by a third-party item of electronic equipment by highlighting in such event, a time delay in acknowledgement of this signal by the key. This method includes, before authorizing the access to and/or starting of the vehicle, additional steps of adapting the amplitude of a coded identification request signal received by the key to reach the detection threshold of the key as soon as possible; measuring the sum of the duration of the emission of the coded interrogation signal and of the duration of the response signal of the electronic key; comparing the sum of the measured durations to a reference duration, and triggering an alarm relating to the conditions of access to and/or starting of the vehicle when the separation between this sum of durations and the reference duration is above a preset threshold.

主权项

1. A method for protecting a hands-free access and/or starting system of a motor vehicle equipped with at least one electronic key, comprising:
a step of emitting a coded identification request (38) emitted by an antenna of a central control unit of said system in the form of a coded interrogation signal (5, 5′) intended for the electronic key (K); a step of the electronic key (K) responding to give its identity (40); and a step of authorizing the access to (46) and/or starting of the vehicle (52), wherein said method furthermore comprises, before the step of authorizing the access to (46) and/or starting of the vehicle (52), additional protection steps consisting in:
adapting the amplitude of at least one sinusoidal signal (Sa) received by the key in the coded identification request step (38) to reach an amplitude detection threshold (15, 16, 17) of the electronic key (K) as soon as possible;stopping said amplitude adaptation (42) as soon as the electronic key (K) is identified in the responding step (40);measuring (43) a sum (Tm, T′m) of durations of transmission of the coded interrogation signal (5, 5′) and of the response signal (7, 7′, 9) of the electronic key;comparing (44, 51) the sum of the measured durations (Tm, T′m) to a reference duration (S, S′);prohibiting the access to and/or starting of the vehicle when a difference between this sum of measured durations (Tm, T′m) and the reference duration (T2, T′2) is above a preset threshold (S, S′); andtriggering alarms (50, 54) when the difference between this sum of measured durations (Tm, T′m) and the reference duration (T2, T′2) is above the preset threshold (S,S′).