Physical Layer Wireless Security via Channel-Adaptive Codeword Spreading
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Solution Overview
Problem
Existing wireless communication security methods are vulnerable when the channel quality between the transmitter and the eavesdropper is equivalent or better than the channel quality between the transmitter and the legitimate receiver, as they rely on shared secret keys and are susceptible to interception, especially in fading channels where channel state information is uncertain.
Innovation Solution
A system and method that uses a secrecy code comprising a first and second security code to encode messages into multiple output codewords, transmitted only when the channel quality between the transmitter and the legitimate receiver exceeds a threshold, ensuring security even if the eavesdropper's channel quality is better, by spreading information bits across multiple independent transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher layer security techniques with shared secret keys are used, then security can be provided for transmissions, but the security is only as good as the key sharing mechanism and becomes problematic when key distribution is compromised
Solution Approach 1:
The patent extracts the security function from the application layer and moves it to the physical layer. Instead of using shared secret keys at higher layers, the system uses physical channel characteristics (fading, multipath) to provide security directly at the transmission level, eliminating the need for complex key distribution mechanisms.
Solution Approach 2:
The patent introduces channel state information and physical layer characteristics as an intermediary between transmitter and receiver. This intermediary enables security without requiring direct key sharing, as the physical channel itself becomes the security mechanism through which only the legitimate receiver can decode the transmission.
2Reliability
If secret keys are shared between transmitter and receiver, then security can be achieved, but the security deteriorates when the key sharing mechanism is vulnerable to interception
Solution Approach 1:
The patent converts the harmful effect of eavesdropping into a beneficial security mechanism. By exploiting the fact that the eavesdropper cannot access the same physical channel characteristics as the legitimate receiver, the system turns the interception attempt into evidence of an unauthorized channel, thereby providing security without vulnerable key sharing.
3Productivity
If messages are transmitted over fading channels, then wireless communication is enabled, but channel state uncertainty makes security more difficult to guarantee
Solution Approach 1:
The patent embraces the dynamic nature of fading channels rather than treating them as static. The system continuously adapts to changing channel conditions by using current channel state information for encoding, allowing security to be maintained dynamically even as channel characteristics change over time.
Solution Approach 2:
The patent implements feedback mechanisms where the receiver provides channel state information back to the transmitter. This feedback loop enables the transmitter to adapt its encoding strategy to current channel conditions, ensuring that security measures remain effective despite fading channel variations.
4Reliability
If channel quality threshold is set high for secure transmission, then security is improved when channel quality between transmitter and eavesdropper is better than or equivalent to legitimate receiver channel
Solution Approach 1:
The patent changes the security parameter from relying on absolute channel quality differences to relying on the statistical characteristics of fading channels. By setting thresholds based on channel quality metrics and using the temporal variations in channel states, the system achieves security without completely sacrificing transmission opportunities.
Data Source
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AI summary
A system and method for securing wireless transmissions is provided. A method for transmitting secure messages by a transmitter includes encoding a message with a secrecy code to produce L output codewords, where L is an integer value greater than one. The secrecy code includes a first security code and a second security code. The method also includes transmitting one of the L output codewords to a communications device when a channel quality of a channel between the transmitter and the communications device satisfies a criterion, and repeating the transmitting for any remaining L-1 output codewords.