Passive Keyless Entry Relay Attack Prevention via Magnetic Field Angle Computation
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Solution Overview
Problem
Passive Keyless Entry (PKE) systems are vulnerable to Relay Station Attacks (RSA), which extend the range of radio signals between a vehicle and its key, allowing unauthorized access and theft, and existing countermeasures require measuring the orientation of magnetic field vectors, which is not feasible in all systems.
Innovation Solution
A passive keyless entry system that uses a plurality of antennas to generate magnetic fields, measures their projection vectors, computes angles between these vectors, and compares them to threshold values to prevent unauthorized access without requiring the exact orientation of magnetic field vectors in 3D space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing countermeasures measure the orientation of magnetic field vectors to prevent relay attacks, then security against relay attacks is improved, but device complexity and measurement requirements increase
Solution Approach 1:
The patent extracts only the essential information needed for security verification - the angle between magnetic field vectors - rather than measuring complete 3D vector orientations. This is achieved by using multiple antennas to measure magnetic field components and computing only the relevant angular relationship, discarding unnecessary orientation data while maintaining security effectiveness
Solution Approach 2:
The patent transitions from measuring full 3D magnetic field vector orientations to measuring angles between vectors in a reduced dimensional space. By using multiple antennas to capture field components and computing angular relationships rather than complete spatial orientations, the system achieves security verification with fewer measurement dimensions and lower complexity
2Reliability
If multiple antennas are used to generate magnetic fields for angle measurement, then relay attack detection capability is improved, but device complexity increases
Solution Approach 1:
The patent makes the multiple antennas serve multiple functions: they simultaneously generate magnetic fields for authentication and provide the spatial diversity needed for angle measurement and relay attack detection. The same antenna array used for normal PKE operation is also used for security verification, eliminating the need for separate dedicated detection hardware
3Measurement precision
If the system computes angles between magnetic field vectors to prevent relay attacks, then security verification accuracy is improved, but computational requirements and processing time increase
Solution Approach 1:
The patent computes only the angle between magnetic field vectors rather than performing complete 3D spatial analysis or measuring all possible vector components. This partial action approach provides sufficient security verification accuracy while significantly reducing computational complexity and processing time compared to full orientation measurement
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
Effectively prevents Relay Station Attacks by generating an authorization signal while avoiding false positives, without needing to measure the exact orientation of magnetic field vectors, thus enhancing security without the limitations of existing systems.
Implementation Method 1
a receiving antenna having three mutually orthogonal coils, a portable transmitter for communicating with the in-vehicle receiver
Data Source
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Figure 3
Figure 4~5
AI summary
A passive keyless entry system (100) including an in-vehicle apparatus (110) installable on a vehicle (100) and a portable apparatus (140). The in-vehicle apparatus (110) includes: a plurality of antennas (111, 112, 113) for generating a plurality of respective magnetic fields (HI, H2, H3), an in-vehicle receiver for communicating with a portable transmitter of the portable apparatus (140), an in-vehicle control unit (115). The portable apparatus (140) includes: a receiving antenna (141) having three mutually orthogonal coils (141x, 141y and 141z), a portable transmitter for communicating with the in-vehicle receiver, a portable control unit (142). The portable apparatus (140) is configured for measuring at least two projections (m1, m2, m3) of the magnetic fields (HI, H2, H3). The in-vehicle control unit (115) or the portable control unit (142) is configured for computing at least one computed angle (αm, αm13, αm23) between two projections (m1, m2, m3) of the magnetic fields (HI, H2, H3). The in-vehicle control unit (115) or the portable control unit (142) is configured for comparing the at least one computed angle (αm, αm13, αm23) with an angular threshold value (αt). The in-vehicle control unit (115) prevents the authorization signal when all the computed angles (αm, αm13, αm23) are lower than angular threshold value (αt).