Smart Key System Dynamic Transmission Strength Relay Attack Prevention
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Solution Overview
Problem
Conventional smart key systems are vulnerable to relay attacks, where a malicious third party can steal a vehicle by relaying a request signal using a repeater, and existing solutions to prevent this often compromise communication performance in noisy environments.
Innovation Solution
The smart key system includes an in-vehicle device and a mobile device that dynamically adjust the transmission strength of response signals based on noise measurements, ensuring the signal is weaker outside the predetermined area to prevent relay attacks while maintaining communication performance by setting the transmission strength lower than the maximum output, even in noisy conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transmission strength is set lower than maximum output to prevent relay attacks, then security is improved, but signal propagation capability in noisy environments worsens
Solution Approach 1:
The system dynamically adjusts transmission strength based on the received request signal rather than using a fixed low power level. The mobile device calculates its response transmission strength as a proportion of the received request signal strength, ensuring that in noisy environments where the request signal is stronger, the response signal is also appropriately stronger to overcome noise interference. This dynamic adjustment maintains security while adapting to environmental conditions.
Solution Approach 2:
The mobile device uses feedback from the received request signal strength to determine the appropriate response signal transmission strength. By measuring the strength of the incoming request signal and calculating the response strength accordingly (e.g., maintaining a 50% power ratio), the system ensures that the response signal has sufficient power to penetrate noisy environments while still being too weak to reach distant relay points. This feedback mechanism resolves the contradiction between security and noise resistance.
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 effectively prevents vehicle theft via relay attacks while maintaining communication performance, even in noisy environments, by adjusting the transmission strength of response signals to be lower than the maximum output, thus enhancing security without degrading communication quality.
Implementation Method 1
a noise measurement unit configured to measure noise in a radio wave band of a main response signal to be wirelessly transmitted by the mobile device
Implementation Method 2
a transmitter configured to be capable of outputting a radio wave by a predetermined strength; and a mobile device configured to be capable of communicating wirelessly with the in-vehicle device
Data Source
AI summary
A smart key system to prevent theft of a vehicle by a relay attack while securing communication performance under a noisy environment, includes an in-vehicle device that measures noise in a radio wave band of a response signal to be wirelessly transmitted by a mobile device; sets a transmission strength of the response signal greater while the noise becomes greater, within a predetermined strength; wirelessly transmits a request signal including a command about the transmission strength into a predetermined area; receives the response signal; and authenticates the mobile device, by first information preregistered for the mobile device, and second information included in the response signal. The mobile device receives the request signal; sets the transmission strength of the response signal, based on the command in the request signal; and wirelessly transmits the response signal including the second information by the set transmission strength when receiving the request signal.