Radio Key Proximity Verification via Signal Propagation Time
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Solution Overview
Problem
Existing methods for verifying the distance between a radio key and a motor vehicle are vulnerable to relay attacks, which manipulate the distance measurement by forwarding signals through intermediate transmitters, making it difficult to reliably authenticate the key's proximity.
Innovation Solution
The method involves using signal propagation time measurements with a control device that sends electromagnetic signals and receives responses to determine the absolute time offset, identifying any time delays indicative of relay attacks, and selectively using transceivers based on the radio key's position to minimize energy consumption and enhance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If signal propagation time measurement is used to detect relay attacks, then security against relay attacks is improved, but device complexity increases due to requiring precise timing measurement capabilities
Solution Approach 1:
The patent introduces a challenge signal as an intermediary mechanism to enable precise timing measurement. The control device sends a challenge signal with a known timestamp, and the radio key responds with this timestamp included in its answer signal. This intermediary timestamp mechanism allows the control device to calculate signal propagation time without requiring complex hardware timing circuits, thus improving security while limiting the increase in device complexity.
Solution Approach 2:
The patent applies preliminary action by embedding the transmission timestamp of the challenge signal into the signal itself before transmission. This pre-prepared timestamp information is then used by the radio key to calculate the answer signal's timestamp, enabling the control device to determine propagation time without real-time complex measurements. This approach improves security through accurate timing while keeping device complexity manageable.
2Reliability
If multiple transceivers are used for signal transmission, then reliability of distance verification is improved, but energy consumption increases
Solution Approach 1:
The patent implements dynamics by making the selection of transceivers adaptive rather than static. The control device dynamically selects one or more transceivers based on the determined position of the radio key. This dynamic adaptation allows the system to maintain reliable distance verification by using only the necessary transceivers for the current situation, thereby reducing energy consumption compared to continuously operating all transceivers while preserving security.
3Use of energy by moving object
If transceivers are selected based on radio key position, then energy consumption is reduced, but measurement precision may be compromised
Solution Approach 1:
The patent applies local quality by making the transceiver selection position-dependent. Different transceivers are activated based on where the radio key is located relative to the motor vehicle. This ensures that the selected transceivers are optimally positioned for measuring the signal propagation time from that specific location, maintaining measurement precision while avoiding the energy waste of activating all transceivers regardless of position.
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 detects relay attacks by exceeding a predetermined signal propagation time criterion, ensuring secure authentication of the radio key's proximity and reducing energy requirements for the key, thereby enhancing security and efficiency.
Implementation Method 1
A respective signal propagation time is then determined for each radio signal on the basis of the radio signal itself and the associated response signal by means of a signal propagation time measurement
Data Source
AI summary
The invention relates to a method for verifying a predefined maximum spatial distance (MAX) of a radio key (11) in relation to a motor vehicle (10), wherein a control device (26) emits at least one electromagnetic radio signal to the radio key (11) by means of a radio device (21) of the motor vehicle (10), and subsequently receives a respective electromagnetic response signal, and determines a respective signal propagation delay for each radio signal, based on the radio signal and the associated response signal by means of a signal propagation delay measurement, and checks whether a predetermined propagation delay criterion (27) is violated by the signal propagation delay, and in the event of a violated propagation delay criterion (27), same signals an exceeding of the propagation delay (28).