Secure Terrestrial Transmitter Positioning via Cryptographic Timing
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Solution Overview
Problem
Existing terrestrial transmitter-based positioning systems are vulnerable to tampering and spoofing, as malicious users can record signal strengths at one location and send them from another, leading to inaccurate positioning without ensuring the authenticity of the mobile device's location.
Innovation Solution
Implementing a secure positioning method using cryptographic functions based on a master clock and secret codes, where transmitters broadcast packets with pseudo-randomly changing frequencies, and mobile devices verify the timing of transmissions to ensure authenticity, only providing position information if the indicated timing matches the expected timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If terrestrial transmitters broadcast standard signals for positioning, then positioning service is available at indoor locations, but the system becomes vulnerable to tampering and spoofing attacks
Solution Approach 1:
The patent applies preliminary action by pre-configuring transmitters with secret codes and establishing expected timing patterns before positioning operations begin. The server stores secret codes for each transmitter and pre-calculates expected transmission timings based on these codes, creating a security framework in advance that prevents spoofing attacks without affecting normal positioning service availability
Solution Approach 2:
The patent implements feedback by having the mobile device measure actual transmission timings and send these measurements to the server, which then compares them against pre-calculated expected timings. This closed-loop feedback mechanism allows the system to verify authenticity continuously and reject spoofed signals while maintaining seamless positioning service for legitimate users
2Productivity
If the system accepts positioning requests from mobile devices without verification, then positioning speed is fast, but position information can be spoofed using recorded data
Solution Approach 1:
The server pre-calculates expected transmission timings for each transmitter based on stored secret codes before receiving any positioning requests. This preliminary preparation allows the server to quickly verify authenticity by simple comparison without performing complex calculations during the positioning request processing, thus maintaining fast positioning speed while ensuring authentication security
Solution Approach 2:
The patent applies partial action by verifying only the critical timing parameter that is essential for authentication, rather than performing comprehensive verification of all signal characteristics. This selective verification approach maintains fast processing speed while providing sufficient security to prevent spoofing with recorded data
3Ease of operation
If transmitters use fixed transmission timing, then mobile devices can easily measure signal strengths, but malicious users can record and replay signals from different locations
Solution Approach 1:
The patent applies dynamics by making transmission timings variable and time-dependent rather than fixed. Each transmitter uses its secret code to generate a specific expected timing pattern that changes over time. Mobile devices still easily measure these dynamic timings, and the server verifies them against the time-varying expected patterns, preventing replay attacks while maintaining measurement simplicity
Solution Approach 2:
The patent changes the timing parameter from a fixed value to a time-dependent variable determined by secret codes. This parameter change allows the system to maintain ease of measurement while introducing temporal variability that prevents spoofing, as recorded signals will have incorrect timings when replayed at different times
Data Source
AI summary
A device with transmitter broadcasts packets including a transmitter identifier via a radio interface with varying timings of transmissions. It determines a current timing of transmissions based on clock signals and a secret code, using a cryptographic function. A mobile device detects radio signals conveying such packets and performs measurements on the signals. It determines a currently used timing of transmissions, assembles a positioning request including the transmitter identifier, results of the measurements and an indication of the timing of transmissions, and transmits the request. A server receives the request. It generates for the transmitter an expected timing of transmissions using a cryptographic function, based on a signal of a master clock and based on a stored secret code assigned to the transmitter. It provides position information as trusted position information only in the case of a match between the indicated and the expected timing of transmissions.