PEPS Relay Attack Detection Using 3D LF Signal Vector Normalization
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Solution Overview
Problem
Current PEPS systems are vulnerable to relay attacks, where thieves extend the range of the LF field to deceive the system into thinking the key fob is in proximity, allowing unauthorized access and start of vehicles, and existing countermeasures are either complex, ineffective, or expensive.
Innovation Solution
A method and system using a 3D LF receiver to measure LF signal levels on x, y, and z-axes, selecting orthogonal or parallel antennas to normalize vectors, and determining if these normalized values are within a predefined range to detect relay attacks, effectively distinguishing between legitimate and relayed signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If relay attack prevention techniques such as time of flight analysis, signal vector checks, and signal superposition are implemented, then relay attack detection capability is improved, but system complexity increases and false positives occur
Solution Approach 1:
The patent extracts and analyzes specific signal characteristics (time of flight, signal strength, vector components) from the complex PEPS communication protocol. By isolating these individual parameters for separate analysis, the system achieves effective relay attack detection without implementing complex multi-parameter analysis algorithms, thus reducing overall system complexity while maintaining detection capability.
Solution Approach 2:
The patent transforms the relay attack detection problem from analyzing complex signal patterns to measuring specific physical parameters (time of flight, signal strength, magnetic field vector components). By changing the detection parameters to these fundamental physical quantities, the system achieves simpler measurement and comparison operations that reduce computational complexity while improving detection reliability.
2Reliability
If existing relay attack countermeasures are implemented, then detection capability is improved, but implementation cost increases
Solution Approach 1:
The patent utilizes the existing PEPS communication infrastructure and standard vehicle antennas to perform relay attack detection. The system uses the same LF antennas already present in the vehicle for both normal key fob communication and for measuring signal characteristics for security verification. This self-service approach eliminates the need for additional dedicated hardware, thereby reducing implementation cost while maintaining detection capability.
3Reliability
If signal vector checks are performed using perpendicular antennas, then relay attack detection is improved, but measurement precision is limited by RSSI dynamic range
Solution Approach 1:
The patent transitions from using perpendicular antenna orientations to using parallel antenna orientations for vector checks. This dimensional change in antenna configuration, combined with parallel processing of multiple antenna signals, overcomes the limitations of RSSI dynamic range by providing additional independent measurement dimensions that improve both detection reliability and measurement precision simultaneously.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the detection of relay attacks by normalizing LF signal vectors across multiple axes, reducing false positives and ensuring accurate authentication, thereby preventing unauthorized vehicle access.
Implementation Method 1
transmitting LF signals from antennas associated with a vehicle to be measured by a key fob having using a three dimensional (3D) LF receiver
Data Source
AI summary
A method and system for detecting if a relay is present in a PEPS system for a vehicle is provided which includes (a) transmitting LF signals from antennas associated with a vehicle to a key fob using a 3D LF receiver to measure the LF signal level on the x, y and z-axes; (b) selecting two or more parallel antennas associated with the vehicle that are orthogonal to the antenna at the PEPS triggering location; (c) normalizing the x, y and z vectors that are measured by the key fob for the selected two or more parallel antennas associated with the vehicle; and (d) determining if the normalized x, y and z vectors for the selected two or more parallel antennas associated with the vehicle are within a predefined range.