GNSS Signal Authentication via PRN Bit Inversion
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Solution Overview
Problem
GNSS open service signals are vulnerable to spoofing attacks, which can lead to erroneous positioning, and existing encrypted signals are not universally available for secure applications, posing a significant risk to critical services like public safety and navigation.
Innovation Solution
Incorporating an authentication mechanism by inverting bits in the pseudorandom noise code of GNSS signals using a cryptographic pseudorandom number generator, with varying positions and numbers of inverted bits per period, and providing decryption keys to receivers to authenticate signals, ensuring secure and spoof-resistant navigation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If encrypted GNSS signals are used to protect against spoofing, then security and resistance to spoofing attacks improve, but device complexity and cost increase
Solution Approach 1:
The patent segments the authentication mechanism by inverting only specific bits (e.g., every 10th bit) of the pseudorandom noise code rather than encrypting the entire signal. This partial modification provides authentication capability while maintaining the simplicity of open service signals for most receivers.
Solution Approach 2:
Instead of using complex encryption to protect signals, the patent inverts specific bits of the pseudorandom noise code to create an authentication mechanism. The inversion pattern itself serves as the authentication key, allowing receivers to verify signal authenticity without needing complex encryption/decryption operations.
2Reliability
If open service signals are modified with authentication bits, then authentication capability improves, but signal operation and compatibility may be compromised
Solution Approach 1:
The patent applies partial action by inverting only a small subset of bits (e.g., every 10th bit) in the pseudorandom noise code. This limited modification provides sufficient authentication capability while minimizing impact on signal compatibility with existing receivers that process the full code sequence.
Solution Approach 2:
The authentication mechanism uses periodic inversion of bits at regular intervals within the pseudorandom noise code period. This periodic pattern creates a predictable authentication signature that receivers can detect and verify without disrupting the continuous operation of the navigation signal.
3Reliability
If multiple inverted bits are used per period, then authentication security improves, but loss of signal information increases
Solution Approach 1:
The patent applies local quality by inverting bits at specific local positions within the pseudorandom noise code (e.g., every 10th bit) rather than randomly or universally inverting bits. This targeted approach provides authentication security at specific locations while preserving the overall information content and navigation functionality of the signal.
Data Source
AI summary
Authentication mechanism is provided to open service signals in Global Navigation Satellite Systems (GNSS), by inverting a plurality of bits in a pseudorandom noise code in a GNSS signal having a predetermined period of a binary bit sequence of N bits. A position of each inverted bit in the binary bit sequence is specified by a serial number generated for each period using a cryptographic pseudorandom number generator, where at least one of the position of the inverted bit and a number of the inverted bits in the period varies period by period. A decryption key is provided to a GNSS receiver, which correlates, using a corresponding cryptographic pseudorandom number generator, the received GNSS signal, and accumulates an amplitude thereof at the inverted bit, thereby determining if the received signal is counterfeit based on the ratio of the inverted bit amplitude with respect to the signal amplitude.