Phase Difference Distance Calculation for Relay Attack Detection

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Solution Overview

Problem

Passive keyless entry systems for vehicles are vulnerable to relay attacks, where intermediaries use relay units to falsely establish communication between the vehicle-mounted device and the mobile device, potentially leading to unauthorized vehicle access and theft.

Innovation Solution

A position detection system that includes multiple vehicle-mounted devices and a mobile device, which transmit and receive distance-calculation signals to determine the phase difference and calculate distances, allowing the system to detect the presence of relay devices by determining if the calculated distances exceed a predetermined threshold, thereby preventing unauthorized communication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If relay units are used to extend communication range, then communication between vehicle-mounted device and mobile device is enabled beyond normal range, but security against relay attacks deteriorates

Engineering Contradiction:

Improvecommunication rangeVSAvoidsecurity

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The system performs preliminary distance verification by calculating the distance between the mobile device and vehicle-mounted device using phase difference measurement before allowing communication. This preliminary check prevents relay attacks by detecting when the calculated distance exceeds the predetermined threshold, blocking unauthorized communication before it can occur.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces physical proximity verification with electromagnetic phase difference measurement for distance calculation. By substituting the mechanical concept of physical closeness with electromagnetic wave phase analysis, the system can accurately detect relay devices that attempt to extend communication range, maintaining security while enabling legitimate long-range communication.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If distance calculation using phase difference is implemented, then relay devices can be detected, but system complexity increases

Engineering Contradiction:

Improverelay attack detectionVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system uses phase difference as an intermediary parameter to detect relay devices. Instead of directly detecting the presence of relay devices, the system measures the phase difference of communication signals, which indirectly reveals the distance information. This intermediary approach simplifies the detection mechanism while maintaining high reliability in relay attack detection.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If multiple vehicle-mounted devices are used for distance calculation, then detection accuracy improves, but device quantity and system complexity increase

Engineering Contradiction:

Improvedistance measurement accuracyVSAvoidnumber of vehicle-mounted devices

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent combines the distance calculation functions of multiple vehicle-mounted devices to improve measurement accuracy. By merging the phase difference measurements from multiple devices, the system achieves more reliable distance verification while sharing the computational load, thereby improving detection accuracy without proportionally increasing system complexity.

Inventive Principle:

Principle #5Merging (Combining)

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 detects and prevents relay attacks by accurately determining the presence of relay devices, ensuring secure communication and preventing unauthorized access to the vehicle.

Implementation Method 1

transmit and receive distance-calculation signals to determine the phase difference and calculate distances

Methodology Applied

Scientific EffectPhase difference measurement:

Data Source

PatentUS7301467B2Position detection system, position detection method therefor, position detection communication device, and communication device

Publication Date: 2007.11.27 SEMICON COMPONENTS IND LLC

AI summary

In a position detection system, a plurality of first communication devices each comprise a transmitter for transmitting a distance-calculation signal for calculating distance to the second communication device; a detector for detecting, by receiving from the second communication device a signal corresponding to the distance-calculation signal, phase difference between the distance-calculation signal when transmitted and the signal corresponding to the distance-calculation signal when received; and a calculator for calculating the distance to the second communication device, based on the phase difference. A second communication device comprises a transmitter for transmitting the signal corresponding to the distance-calculation signal. The position detection system comprises a determining unit for determining whether the multiple distances are below a predetermined distance; and a position detector for detecting the position of a relay device corresponding to the multiple distances when the determining unit has determined that the multiple distances are at or above the predetermined distance.