Motion-Activated Transponder for Relay Attack Prevention
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Solution Overview
Problem
Keyless vehicle entry systems are vulnerable to relay attacks and suffer from high power consumption due to continuous signal emission and the transponder unit's constant readiness to receive signals, even when no authorized device is present.
Innovation Solution
Incorporating a motion sensor in the transponder unit to detect movement and transmit motion information, allowing the system to activate the vehicle only when the transponder is moved, and transitioning to a low-power idle state when not in use, with secure communication through encryption and signing to prevent unauthorized access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transmission unit emits signals at regular intervals and the transponder unit remains constantly ready to receive signals, then the vehicle can be reliably accessed by authorized users, but the power consumption in both the vehicle and transponder unit increases significantly
Solution Approach 1:
The transponder unit switches between active and idle states periodically, only becoming active when motion is detected. This periodic activation reduces power consumption while maintaining reliability, as the system only consumes full power when actually needed for authentication
Solution Approach 2:
The motion sensor automatically detects when the transponder unit is moved and triggers activation without external intervention. This self-service mechanism ensures the system becomes active exactly when needed (when carried by user) without requiring continuous power consumption
2Reliability
If the transponder unit remains constantly active to receive signals, then authorized access is maintained, but the system becomes vulnerable to relay attacks by third parties
Solution Approach 1:
The transponder unit dynamically changes its operational state based on motion detection. It transitions from a static constantly-active state to a dynamic state where it activates only when moved, making relay attacks ineffective since the transponder cannot be continuously intercepted
Solution Approach 2:
The motion sensor detects movement in advance and triggers activation before any authentication attempt can occur. This preliminary detection prevents relay attacks by ensuring the transponder only responds when actually present with the user, not when being intercepted remotely
3Reliability
If the transmission unit continuously emits signals to ensure vehicle access, then authorized users can reliably access the vehicle, but the power consumption in the vehicle increases
Solution Approach 1:
The transmission unit emits signals periodically rather than continuously, synchronized with the transponder's active periods. This reduces overall power consumption while maintaining access reliability, as signals are only transmitted when the transponder is likely to be active
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
Enhances security against relay attacks and reduces power consumption by activating the vehicle only when the transponder is in motion and transitioning to a low-power state when not in use, while ensuring secure communication.
Implementation Method 1
the transponder unit comprises a motion sensor which is designed to detect a movement of the transponder unit and to generate motion information
Implementation Method 2
These are, for example, electromagnetic signals in the LF (Low Frequency) or HF (High Frequency) band
Data Source
AI summary
An entry system includes a transponder unit and a transmission unit which is arranged in an object. The transmission unit is designed to transmit a request to the transponder unit, and the transponder unit includes a motion sensor which is designed to detect a movement of the transponder unit and to generate motion information. The transponder unit is designed to transmit, in a first operating state, to the transmission unit, in response to the request, a reply containing the motion information, wherein the transmission unit is designed to decide on the basis of the motion information whether to activate the object.