BLE Transceiver Power Attenuation for Relay Attack Prevention
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Solution Overview
Problem
Bluetooth Low Energy (BLE) systems used for keyless vehicle entry face challenges in distinguishing 'fob'-to-vehicle distances, leading to increased costs and complexity due to existing angle-of-arrival and time-of-flight features.
Innovation Solution
A method and system that utilize a first transceiver configured to transmit and receive BLE signals according to the BLUETOOTH Core Specification version 4.2 and later, with a controller circuit that attenuates RF signals to reduce the communication range from 600m to 0.4m to 2m, enabling secure vehicle access by limiting communication range and reducing interference from distant devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If BLE signals are transmitted at high power to extend communication range, then transmission range is improved, but security and interference control deteriorate
Solution Approach 1:
The system dynamically adjusts the transmit power level based on the operational state. During vehicle sensing mode, the system uses higher power levels to detect key fobs from greater distances. During keyless entry mode, the system reduces power to a lower level to limit communication range and prevent relay attacks, thereby adapting the communication characteristics to security requirements
Solution Approach 2:
The patent changes the power parameter of BLE transmissions to resolve the contradiction. By implementing multiple power levels (higher for sensing, lower for entry), the system can extend range when needed while maintaining security when required, directly addressing the trade-off between communication range and security/interference control
2Measurement precision
If angle-of-arrival and time-of-flight features are implemented to distinguish distances, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and removes the complex angle-of-arrival and time-of-flight measurement features from the system. Instead of implementing these sophisticated distance measurement techniques, the system uses a simpler approach with multiple fixed power levels and basic signal detection, thereby reducing device complexity and cost while still providing adequate distance-based access control
Solution Approach 2:
The system replaces expensive, complex measurement hardware and algorithms with simpler, more cost-effective solutions. By using basic BLE signal detection at different power levels rather than sophisticated AoA/ToF measurement capabilities, the system achieves distance distinction with lower complexity and reduced cost
3Ease of operation
If communication range is extended to allow remote keyless entry, then ease of operation is improved, but vulnerability to relay attacks increases
Solution Approach 1:
The system employs periodic transmission at different power levels to balance ease of operation and security. By alternating between higher power transmissions (enabling remote operation) and lower power transmissions (limiting relay attack window), the system maintains usability while reducing vulnerability to relay attacks through time-based power modulation
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
The solution effectively reduces the communication range between wireless devices, enhancing vehicle security by limiting potential interference and allowing secure communication within a controlled range, thus improving the reliability of keyless entry systems.
Implementation Method 1
A controller circuit communicatively coupled with the first transceiver and configured to attenuate the first RF signals to transfer the first RF signals at a second transmission level lower than the first transmission level
Data Source
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AI summary
A system includes a first transceiver and a controller circuit. The first transceiver is configured to transmit first radio frequency (RF) signals. The first transceiver is further configured to output the first RF signals at a first transmission level corresponding to a first transmission range. The controller circuit is communicatively coupled with the first transceiver. The controller circuit is configured to attenuate the first RF signals to transfer the first RF signals at a second transmission level lower than the first transmission level. The second transmission level corresponds to a shorter transmission range than the first transmission range. The controller circuit detects a presence of at least one second transceiver within the shorter transmission range using the first RF signals transmitted at the second transmission level.