Channel-Based Secret Key Sharing Across Multiple FDD Frequency Bands
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Solution Overview
Problem
Wireless communication systems face security vulnerabilities due to eavesdropping attacks, particularly in frequency division duplex (FDD) mode, where channel reciprocity is lost, and transitioning to time division duplex (TDD) involves significant infrastructure changes and compatibility issues.
Innovation Solution
A method for generating a channel-based shared secret key using different frequency bands for transmitting and receiving known bits, ensuring that illegitimate users cannot directly access channel characteristics by performing forward transmissions twice in different frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cryptography-based algorithms are used to secure wireless communication, then data confidentiality is improved, but power consumption and hardware complexity increase
Solution Approach 1:
The patent replaces traditional cryptography-based security mechanisms with physical layer security mechanisms that exploit channel characteristics. Instead of using complex cryptographic algorithms that consume significant power, the system uses the inherent physical properties of wireless channels (multipath fading, reciprocity) to generate and share secret keys, thereby reducing power consumption while maintaining security.
Solution Approach 2:
The patent changes the fundamental approach from using mathematical complexity (cryptography) to using physical channel parameters (channel impulse response, multipath characteristics) for security. By extracting secret information from channel parameters rather than cryptographic computations, the system achieves security with reduced power consumption and hardware complexity.
2Adaptability or versatility
If channel-based secret key sharing is implemented in FDD mode, then communication flexibility is improved, but security is worsened due to loss of channel reciprocity
Solution Approach 1:
The patent addresses the security issue in FDD mode by moving from a single-channel approach to a multi-dimensional approach using multiple frequency bands. Instead of relying solely on channel reciprocity in one frequency band, the system transmits known bits across multiple frequency bands and uses the combined channel characteristics from all bands to generate the secret key, thereby maintaining security while preserving FDD flexibility.
Solution Approach 2:
The patent creates a composite security mechanism by combining channel characteristics from multiple frequency bands. Instead of using a single channel response, the system integrates information from multiple frequency bands to form a composite channel signature that is more resistant to eavesdropping attacks, thereby maintaining security in FDD mode.
3Reliability
If known bits are transmitted over wireless channels for key generation, then secret key sharing is enabled, but channel responses become accessible to illegitimate users
Solution Approach 1:
The patent introduces multiple frequency bands as intermediaries in the key generation process. Instead of directly transmitting information that reveals channel responses, the system uses known bits transmitted over multiple frequency bands as intermediaries. The legitimate users combine the channel characteristics from all frequency bands to generate the secret key, while an eavesdropper would need to intercept and process all frequency bands simultaneously, making the attack significantly more difficult.
Solution Approach 2:
The patent segments the channel information across multiple frequency bands rather than concentrating all channel characteristics in a single band. By dividing the key generation process across multiple frequency segments, the system ensures that an eavesdropper would need to capture and process all segments to reconstruct the channel response, thereby protecting the secret key generation from eavesdropping attacks.
Data Source
Figure 1~2b
Figure 3~5
Figure 6A~6C
AI summary
Techniques and methods are described to generate a shared secret key using channel characteristics between a transmitting device and a receiving device. A public key is transmitted to a communication device over a first wireless channel and a second wireless channel that is different from the first wireless channel. From the communication device, a first signal and a second signal both carrying the public key are received over the first wireless channel and the second wireless channel, respectively. Based on the first signal and the public key, a first channel response is calculated and, based on the second signal and the public key, a second channel response is calculated. The secret key is determined based on the first and second channel response. In this way, the generation of a channel-based shared secret key becomes more secure and robust against eavesdropping of illegitimate users, allowing for secure communication.