Relay Attack Mitigation Using Phase-Based Time-of-Flight
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Solution Overview
Problem
Current remote keyless entry systems and Phone-as-a-Key systems are vulnerable to relay attacks, which can deceive vehicles into thinking the key fob is nearby by amplifying RF signals, due to their reliance on signal strength for distance determination, leading to inadequate protection and high costs for sophisticated solutions.
Innovation Solution
Implementing an enhanced Time-of-Flight (ToF) calculation using phase measurements and RF fingerprinting, with blockchain-based decentralized analysis, to accurately determine the key fob's distance from the vehicle and prevent relay attacks by measuring phase differences and unique RF characteristics, while minimizing equipment costs and bandwidth usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If signal strength is used to determine distance, then the system is simple and low cost, but the system becomes vulnerable to relay attacks
Solution Approach 1:
The patent changes the measurement parameter from signal strength (RSSI) to Time-of-Flight (ToF) based on phase measurements. This allows accurate distance determination that cannot be spoofed by relay attacks, as the round-trip time of the signal is physically determined by the actual distance. The system calculates distance using d = c × ToF / 2, where c is the speed of light, making it impossible for attackers to fake proximity without physically being near the vehicle.
2Reliability
If sophisticated relay attack prevention solutions are implemented, then security is improved, but the cost increases significantly
Solution Approach 1:
The patent replaces complex cryptographic authentication systems and hardware security modules with a physics-based solution using Time-of-Flight measurements. By utilizing the fundamental physical constant (speed of light) and measuring signal propagation time, the system achieves security without requiring expensive cryptographic processors or specialized security hardware, thereby reducing overall system cost while maintaining high security standards.
3Measurement precision
If Time-of-Flight calculation using phase measurements is implemented, then distance measurement accuracy is improved, but communication bandwidth consumption increases
Solution Approach 1:
The patent measures phase differences at multiple frequency offsets (e.g., -500 kHz, 0 Hz, +500 kHz) to calculate Time-of-Flight, but only uses the necessary minimum set of measurements to achieve accurate distance determination. This partial measurement approach provides sufficient precision for security purposes without unnecessarily consuming excessive bandwidth, balancing measurement accuracy with communication efficiency.
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 prevents relay attacks by accurately determining the key fob's distance and authenticating RF signals, reducing the risk of unauthorized access and minimizing equipment costs, while maintaining communication bandwidth.
Implementation Method 1
performing a time-of-flight calculation based on a phase measurement to determine a distance between the key fob and the vehicle
Data Source
AI summary
This disclosure describes systems, methods, and devices related to enhanced time of flight (ToF) calculation using phase measurements. A device may identify a radiofrequency (RF) signal received from a vehicle key, wherein the RF signal comprises a command associated with a vehicle. The device may select a first subset of a frequency bandwidth. The device may perform a first time-of-flight calculation associated with the RF signal using a phase shift measurement on a first subset of frequency bandwidth. The device may determine a distance between the vehicle key and the vehicle based on the first time-of-flight calculation. The device may compare the distance to a predetermined threshold. The device may determine a status of the RF signal based on the comparison.