Electromagnetic Fingerprints for Relay-Resistant Proximity Detection

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Solution Overview

Problem

Existing vehicle keyless entry systems are vulnerable to relay attacks, which allow unauthorized access by simulating a smartphone's proximity to unlock the vehicle, necessitating a robust method to ensure devices are in proximity before unlocking.

Innovation Solution

Devices generate electromagnetic wave fingerprints of their environments and compare these fingerprints to determine proximity, using a matching score to confirm they are in close proximity, thereby resisting relay attacks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If traditional proximity detection methods are used, then ease of operation is improved, but security is worsened due to vulnerability to relay attacks

Engineering Contradiction:
Improveproximity detectionVSAvoidsecurity
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The patent introduces electromagnetic wave fingerprints as an intermediary verification mechanism. Instead of directly trusting proximity detection signals, the system uses environmental electromagnetic wave patterns (WiFi, Bluetooth, cellular signals) as a mediator to indirectly verify that devices are truly in physical proximity, thereby blocking relay attacks without complicating user interaction

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The system performs preliminary verification by comparing electromagnetic wave fingerprints before authorizing the proximity-based unlocking operation. This preliminary check ensures that the devices are genuinely in proximity before the actual access operation occurs, preventing relay attacks from succeeding

Inventive Principle:
Principle #10Preliminary action

2Reliability

If relay attack prevention measures are implemented, then security is improved, but device complexity increases

Engineering Contradiction:
ImprovesecurityVSAvoidsystem complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent makes existing electromagnetic wave receiving components (WiFi, Bluetooth, cellular antennas) serve a dual function: their primary communication function and a secondary proximity verification function. By analyzing the same environmental electromagnetic waves that devices naturally receive, the system achieves security enhancement without adding dedicated hardware or significantly increasing system complexity

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses the devices' own existing electromagnetic wave reception capabilities to perform proximity verification. Each device independently collects and analyzes environmental electromagnetic wave patterns, making the security verification self-contained and eliminating the need for additional external verification systems

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP4064740B1Method of proximity detection between two devices
Publication Date: 2025.08.13 NAGRAVISION SRL
  • EP4064740B1 patent drawingFigure 1
  • EP4064740B1 patent drawingFigure 2~3
  • EP4064740B1 patent drawingFigure 4

AI summary

The method of proximity detection between a first and a second device (DVC1, DVC2), carried out by the first device (DVC1), comprises the steps of collecting a first information on exposure of the first device (DVC1) to electromagnetic waves; receiving a second information on exposure of the second device (DVC2) to electromagnetic waves from the second device (DVC2); determining a matching information between the first information on exposure and the second information on exposure and detecting either proximity or non-proximity between the first and the second device (DVC1, DVC2) based on the matching information.