Acoustic Proximity Verification for Secure Access Control
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Solution Overview
Problem
Existing electronic access control systems using radio signal transmission face challenges such as unintentional unlocking of multiple doors due to wide communication ranges, user interaction requirements, and the risk of fraudulent relaying attacks, particularly with Bluetooth Low Energy (BLE) technology.
Innovation Solution
An access control system that uses acoustic signal propagation time to verify the proximity of a portable user device, mitigating fraudulent relaying attacks by determining if the device is within a pre-determined distance range, and employing a BLE interface to reduce costs and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If radio signal transmission with a communication range exceeding one meter is used, then the communication range is improved, but the risk of fraudulent relaying attacks increases
Solution Approach 1:
The patent introduces acoustic signals as an intermediary verification mechanism. The access control system emits an acoustic signal that the portable user device must detect and relay back. This acoustic intermediary creates a physical proximity requirement that prevents fraudulent relaying attacks, as the acoustic signal cannot be transmitted over long distances like radio signals can.
Solution Approach 2:
The system performs a preliminary acoustic signal exchange before granting access based on radio communication. The access control system first emits an acoustic signal, verifies the portable device detected it within close proximity, and only then proceeds with the authorization decision. This preliminary action ensures the user is physically present before allowing access.
2Measurement precision
If the portable user device is prompted to select one of the electronic door locks via a user interface, then the accuracy of door selection is improved, but the operation time increases
Solution Approach 1:
The system uses the portable user device's own capabilities (acoustic signal detection and radio communication) to automatically determine which door to unlock. The device self-identifies the nearest access control system through acoustic signal propagation time measurement, eliminating the need for manual user selection and reducing operation time while maintaining accurate door selection.
3Measurement precision
If additional hardware components for location and directionality detection are added, then the door selection accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent makes the portable user device multi-functional by using its existing acoustic capabilities (microphone/speaker) for both audio processing and proximity-based door selection. The access control system's electroacoustic transducer serves dual purposes: access authentication and location determination. This eliminates the need for separate location detection hardware while maintaining door selection accuracy.
Solution Approach 2:
The patent replaces complex mechanical or dedicated electronic location detection systems with acoustic signal propagation time measurement. By using sound wave travel time, the system determines distance and selects the nearest door without requiring additional sensors, cameras, or complex positioning hardware.
4Reliability
If electroacoustic transducers are added to the access control system, then the security against fraudulent attacks is improved, but the manufacturing cost increases
Solution Approach 1:
The patent uses inexpensive electroacoustic transducers (speakers/microphones) that are already mass-produced for consumer electronics. These low-cost components provide robust security against fraudulent relaying attacks by enforcing physical proximity through acoustic signal verification, achieving high security at low manufacturing cost.
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 solution allows for efficient and secure access control with reduced user interaction, preventing unintentional unlocking and mitigating fraudulent attacks, while maintaining low power consumption and moderate additional costs for implementation.
Implementation Method 1
a propagation time of an acoustic signal between an access control system and a portable user device is determined. The propagation time is indicative of whether the portable user device is located within a pre-determined distance range from the access control system
Data Source
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AI summary
An access control system (10) comprises a radio interface (12) configured to communicate with a portable user device (20), an electroacoustic transducer (13, 14), and a control circuit (11). The control circuit (11) is configured to selectively activate an actuator (7) in an access grant procedure based on a propagation time of the acoustic signal between the electroacoustic transducer (13, 14) and the portable user device (20).