Distance Upper Bound Determination via Round-Trip Time
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Solution Overview
Problem
Existing methods for determining the distance between devices are inaccurate due to wide variance in signal strength measurements and vulnerability to relay attacks, where malicious devices can pretend to be closer than they actually are.
Innovation Solution
A method that calculates a distance upper bound by measuring round-trip times and accounting for processing delays using a processing time multiplier, allowing for more accurate distance determination by isolating transit time independent of processing time, and using the speed of light to establish an upper bound on the distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal strength measurements are used to determine distance between devices, then distance estimation can be obtained, but the measurement accuracy deteriorates due to wide variance in signal strength
Solution Approach 1:
The patent replaces signal strength-based distance estimation with a time-based measurement system. Instead of relying on variable signal strength measurements, the system uses round-trip time measurements of challenge-response messages, which provide a more reliable and accurate distance determination by measuring the actual time taken for signals to travel between devices.
Solution Approach 2:
The patent changes the measurement parameter from signal strength to time. By measuring the round-trip time of messages between devices and accounting for processing delays, the system achieves more accurate distance determination. The formula distance = (round_trip_time - processing_delay) × speed_of_light / 2 transforms the measurement approach fundamentally.
2Device complexity
If simple round-trip time measurement is used to determine distance, then the measurement process is simplified, but the accuracy deteriorates due to processing time variance
Solution Approach 1:
The patent segments the round-trip time measurement into distinct components: transmission time, processing time, and reception time. By introducing challenge and response messages with known processing delays, the system can isolate and calculate the actual transmission time, thereby achieving accurate distance measurement while maintaining process simplicity.
Solution Approach 2:
The patent implements a feedback mechanism where the target device responds to challenges with a known processing delay. The verifier device uses this feedback (the response time) to calculate the actual transmission time by subtracting the known processing delay from the total round-trip time, thereby achieving accurate distance measurement.
3Reliability
If distance measurement methods are implemented, then security can be enhanced, but vulnerability to relay attacks persists where malicious devices can pretend to be closer
Solution Approach 1:
The patent implements preliminary verification by measuring the actual physical distance between devices before allowing transactions. By establishing a distance upper bound through time-based measurement, the system can prevent relay attacks by ensuring that devices are within the required proximity threshold before proceeding with any secure operations.
Solution Approach 2:
The patent introduces challenge-response messages as intermediaries to verify the actual physical distance between devices. These messages act as mediators that carry timing information, allowing the system to detect relay attacks by comparing the measured distance against the required proximity threshold, thereby thwarting malicious devices that attempt to pretend to be closer.
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 provides a reliable and accurate method to determine the upper bound of the distance between devices, effectively thwarting relay attacks and improving security in communication systems by ensuring devices are physically close for transactions.
Implementation Method 1
multiplying the transit time measurement by the speed of light. The distance upper bound may be an upper bound for a distance between the verifier device and the target device
Data Source
AI summary
A method for determining a distance upper bound by a verifier device is described. The method includes measuring a first round-trip time to receive a first response from a target device corresponding to a first message sent to the target device. The method also includes measuring a second round-trip time to receive a second response from the target device corresponding to a second message sent to the target device, the second response being delayed by a processing time multiplier. The method further includes determining a transit time measurement based on the first round-trip time, the second round-trip time and the processing time multiplier. The method additionally includes determining the distance upper bound based on the transit time measurement.