Method and system for relay attack prevention

A method of detecting if an LF noise source is present in a PEPS system for a vehicle, the method comprising:

• (a) transmitting a challenge signal including an LF telegram and CW signals from one or more antennas associated with a vehicle to a key fob, the CW signals being measured by the key fob;
• and
• (b) determining if the CW signals measured by the key fob meet one or more criteria based on the predetermined differences in the magnetic field distribution between:
• (i) the magnetic field strength values associated with one or more antennas on the vehicle within the PEPS operating regions;
• and
• (ii) the magnetic field strength values associated with one or more antennas on the vehicle within the PEPS operating regions when an LF noise source is present;
• wherein predefined magnetic field strength value ranges, which are acceptable, are obtained by a predetermined comparison of magnetic field strength values, under normal use between the vehicle and key fob without a relay, and other magnetic field strength levels, which are obtained when a relay is inserted between the vehicle and the key fob.

A system for detecting if a relay is present in a PEPS system for a vehicle, comprising:

• one or more antennas associated with the vehicle for transmitting a challenge signal from the one or more antennas to a key fob;
• and
• one or more controllers, each of which is configured to perform the following:
• (a) transmit the challenge signal including an LF telegram and CW signals from one or more antennas associated with a vehicle to a key fob, the CW signals being measured by the key fob;
• and
• (b) determine if the CW signals measured by the key fob meet one or more criteria based on the predetermined differences in the magnetic field distribution between:
• (i) the magnetic field strength values associated with one or more antennas on the vehicle within the PEPS operating regions;
• and
• (ii) the magnetic field strength values associated with one or more antennas on the vehicle at the relay transmitter location when a relay is present;
• wherein predefined magnetic field strength value ranges, which are acceptable, are obtained by a predetermined comparison of magnetic field strength values, under normal use between the vehicle and key fob without a relay, and other magnetic field strength levels, which are obtained when a relay is inserted between the vehicle and the key fob.

A system for detecting if an LF noise source is present in a PEPS system for a vehicle, comprising:

• one or more antennas associated with the vehicle for transmitting a challenge signal from the one or more antennas to a key fob, wherein the CW signals are measured by the key fob;
• and
• one or more controllers, each of which is configured to perform the following:
• (a) transmitting the challenge signal including an LF telegram and CW signals from one or more antennas associated with a vehicle to a key fob;
• and
• (b) determining if the CW signals measured by the key fob meet one or more criteria based on the predetermined differences in the magnetic field distribution between:
• (i) the magnetic field strength values associated with one or more antennas on the vehicle within the PEPS operating regions;
• and
• (ii) the magnetic field strength values associated with one or more antennas on the vehicle within the PEPS operating regions when an LF noise source is present;
• wherein predefined magnetic field strength value ranges, which are acceptable, are obtained by a predetermined comparison of magnetic field strength values, under normal use between the vehicle and key fob without a relay, and other magnetic field strength levels, which are obtained when a relay is inserted between the vehicle and the key fob.

A method of obtaining data sets and establishing criteria for use in detecting if a relay is present in a PEPS system for a vehicle, the method comprising:

• (a) transmitting a challenge signal including an LF telegram and CW signals from one or more antennas associated with a vehicle to a key fob within a PEPS operating region;
• (b) measuring the magnetic field strength values associated with the challenge signal from a plurality of locations within a PEPS operating region and storing the results as a first data set;
• (c) inserting a relay between the vehicle and the key fob;
• (d) transmitting a challenge signal including an LF telegram and CW signals from one or more antennas associated with a vehicle to a key fob at the relay transmitter when a relay is in place;
• (e) measuring the magnetic field strength values associated with the challenge signal from a plurality of locations at the relay transmitter and storing the results as a second data set;
• (f) comparing the first and second data sets;
• and
• (g) generating one or more criteria based on the comparison of the two data sets;
• wherein predefined magnetic field strength value ranges, which are acceptable, are obtained by a predetermined comparison of magnetic field strength values, under normal use between the vehicle and key fob without a relay, and other magnetic field strength levels, which are obtained when a relay is inserted between the vehicle and the key fob.

A method of obtaining data sets and establishing criteria for use in detecting if an LF noise source is present in a PEPS system for a vehicle, the method comprising:

• (a) transmitting a challenge signal including an LF telegram and CW signals from one or more antennas associated with a vehicle to a key fob within a PEPS operating region;
• (b) measuring the magnetic field strength values associated with the challenge signal from a plurality of locations within a PEPS operating region and storing the results as a first data set;
• (c) inserting an LF noise source in proximity to the key fob within a PEPS operating region;
• (d) transmitting a challenge signal including an LF telegram and CW signals from one or more antennas associated with a vehicle to a key fob within a PEPS operating region where an LF noise source is in close proximity to the key fob;
• (e) measuring the magnetic field strength values associated with the challenge signal from a plurality of locations within a PEPS operating region where an LF noise source is in close proximity to the key fob and storing the results as a second data set;
• (f) comparing the first and second data sets;
• and
• (g) generating one or more criteria based on the comparison of the two data sets;
• wherein predefined magnetic field strength value ranges, which are acceptable, are obtained by a predetermined comparison of magnetic field strength values, under normal use between the vehicle and key fob without a relay, and other magnetic field strength levels, which are obtained when a relay is inserted between the vehicle and the key fob.