Covert Clock Synchronization Using Ambient RF Signals
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Solution Overview
Problem
Current clock synchronization methods, relying on RF emissions, are vulnerable to jamming and detection by adversaries, making them unreliable in critical scenarios where accurate and covert synchronization is necessary.
Innovation Solution
A system that uses commercial or military RF signals emitted by unrelated parties for synchronization, where a Synchronization Authority time-tags signal peaks and sends them to an Installation, which calculates local clock skew using the time of arrival and phase shift, allowing for covert and accurate synchronization without emitting RF signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ground-based synchronization methods (such as NIST WWVB) are used, then accurate clock synchronization is achieved, but the synchronization authority emits RF signals that can be easily tracked or jammed by adversaries
Solution Approach 1:
The system converts the presence of RF signals (which normally indicate a vulnerable synchronization source) into a benefit by using any emitted signals (including adversary jamming signals) as the synchronization reference. The Synchronization Authority time-tags peaks of received RF signals and shares these time tags for synchronization, turning the very signals that could be used for jamming into the basis for accurate, covert synchronization.
Solution Approach 2:
The system uses existing RF emissions from unrelated parties (commercial TV/radio signals, military signals, or even adversary jamming signals) for synchronization without requiring a dedicated synchronization transmitter. The Synchronization Authority passively receives and processes these ambient signals, eliminating the need for active RF emission from the synchronization source itself.
2Ease of operation
If the synchronization authority emits RF signals for synchronization, then time synchronization can be provided, but the location of the synchronization authority becomes discoverable and vulnerable to adversaries
Solution Approach 1:
The Synchronization Authority uses passively received RF signals from unrelated parties rather than actively transmitting synchronization signals. This eliminates the need for a dedicated synchronization transmitter, making the system mobile and concealable while still providing accurate time synchronization through time-tagged signal peaks.
Solution Approach 2:
The system can use any RF signal source (commercial TV/radio, military signals, adversary jamming signals) as the synchronization reference. This universal approach to signal sourcing eliminates the need for dedicated synchronization infrastructure and enables covert, mobile deployment of the synchronization authority.
Data Source
AI summary
A signal is emitted by an unrelated, non-cooperating party. The SA scans this spectrum, and selects and filters to a portion of the signal emitted. The SA, using its internal clock, time tags a sequence of peaks of the time domain of the filtered signal. The SA sends (over the internet or other method) the time tagged peaks, frequency and location of the emission to the IN. The IN receives the message from the SA. It compares the peaks with its own data, collected using its local antenna at the specified frequency. The IN uses its location, and the location encoded in the message, to compute the different time of arrival of the signal, and uses the locally found peaks at that frequency to determine a "phase shift." The phase shift is used to calculate the local clock skew. The SA repeats step 2, selecting a different frequency.