Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

IEEE Communications Letters

Key Exchange for Two-Way Untrusted Relaying Systems Through Constellation Overlapping

Weijie Li, Mengjie Huang, Xianhui Lu

Published Jan 15, 2024• 4 citations
Publisher

Abstract

This letter proposes a key exchange scheme for the untrusted relay system, where the relay not only assists in message transmission but also tries to recover messages. Terminal users initiate the process by transmitting a local key and utilize constellation overlapping techniques to create an overlapped constellation at the relay nodes, which increases the decoding error rate for relay eavesdropping but still poses a risk of key leakage. To address this, we propose a fine-grained entropy extraction algorithm that quantifies the overlapped constellation points into key bits, which are uniformly random bits from the relay’s perspective. In the constellation overlapping scenario, we can estimate the number of instances where the relay cannot distinguish. Leveraging this, our algorithm achieves remarkable levels of entropy utilization. QPSK enables perfect lossless entropy extraction, while other QAM modulation schemes can achieve a utilization rate of up to 96%.

DOI
10.1109/lcomm.2024.3354063

Related papers

Towards Enhanced Security for Two-Way Untrusted Relaying Systems: A Constellation Overlapping Scheme

Hongbin Xu, Li Sun, Fan Li

This paper proposes a constellation overlapping scheme to secure two-way untrusted relaying systems, where the relay acts as both a helper facilitating data transmission and an eavesdropper intercepting users' messages. A truncated-channel-inversion based approach is developed to make the signals transmitted from two users experience the same equivalent channel, thereby realizing full constellation overlapping at the relay. Consequently, it is extremely difficult for the relay to recover the users' individual signals, and data confidentiality is thus protected. The achieved error floor level at the untrusted relay is analyzed, and the truncation thresholds are optimized to maximize the sum rate for end-to-end information exchange. Simulation results demonstrate the superiority of our scheme in terms of security and transmission efficiency compared with the existing alternatives.

International Conference on Communications•May 1, 2018•6 citations

Unequal Secrecy Protection for Untrusted Two-Way Relaying Systems: Constellation Overlapping and Noise Aggregation

Li Sun, Hongbin Xu

This paper studies the secure information exchange of two-way relaying systems, where two terminal users communicate bi-directionally with the assistance of an untrusted relay. Each user is assumed to have two messages with distinct priorities: high priority and low priority. The high-priority messages (HPM) are first transmitted, for which we propose a constellation overlapping scheme such that the received signals at the relay overlap with each other and a high error floor is created to prevent the untrusted relay from deciphering the information. Upon the completion of HPM exchange, each user sends its low-priority message (LPM) by superposing it onto the previously decoded HPM from the other user. By exploiting the difference between the error patterns for HPM at the terminal users and the relay, channel noises in various time slots can be aggregated at the relay to secure the LPM transmission. The symbol error probability (SEP) at the terminal users as well as the untrusted relay is analyzed, from which it is shown that HPM is guaranteed to have greater reliability and higher secrecy level than that of LPM. However, the transmission of LPM enjoys lower implementation complexity and reduced system overhead, which fully demonstrates that the message-prioritization-based unequal secrecy protection framework can realize a good performance-complexity tradeoff. Simulation results exhibit the superiority of the proposed design compared to the existing competing solutions.

IEEE Transactions on Vehicular Technology•Jul 31, 2018•10 citations

Encryption Over the Air: Securing Two-Way Untrusted Relaying Systems Through Constellation Overlapping

Hongbin Xu, Li Sun

This paper proposes a novel technique called constellation overlapping to secure two-way untrusted relaying systems. We first consider the symmetric case where two terminal users adopt the same modulation type. For this case, a truncated-channel-inversion-based approach is developed to make the signals from different users experience the same equivalent channel, thereby realizing full constellation overlapping at the relay. Consequently, an error floor is created at the untrusted relay, and data confidentiality is protected. Then, the asymmetric case is investigated, where different modulations are employed at the two users and the constellation overlapping cannot be realized. To address this issue, we develop a constellation virtualization method, which exploits the intrinsic user-cooperation mechanism to “virtualize” two identical constellations at the two users. In this manner, the constellation overlapping effect can still be achieved, without sacrificing much reliability performance. We optimize the truncation threshold to maximize the sum rate for end-to-end information exchange, and design the bit-to-symbol mapping criterion and the signal detection method as well. Unlike the existing physical layer security approaches that guarantee secrecy with additional resource consumptions, this method realizes security enhancement by letting different users mutually encrypt their signals over the air, which is more resource-efficient.

IEEE Transactions on Wireless Communications•Oct 19, 2018•33 citations

Message-Prioritization Based Unequal Secrecy Protection for Untrusted Two-Way Relaying Networks

Li Sun, Hongbin Xu, Fan Li

This paper proposes a message-prioritization based unequal secrecy protection framework for untrusted two- way relaying networks, where two terminal users communicate bidirectionally with the assistance of an untrusted relay. Each user is assumed to have two messages with distinct priorities: high priority and low priority. The high priority messages (HPM) are first transmitted, for which we devise a constellation overlapping method such that the received signals at the relay overlap with each other and a high error floor is created to prevent the untrusted relay from deciphering the information. Upon the completion of HPM exchange, users transmit their low priority messages (LPM) using a noise aggregation approach. To be specific, each user superposes its LPM onto the previously decoded HPM from the other user. By exploiting the difference between the error patterns for HPM at the terminal users and the relay, channel noises in various time slots can be aggregated at the relay to secure the LPM transmission. It is shown from simulation results that HPM is guaranteed to have greater reliability and higher secrecy level than that of LPM. However, the transmission of LPM enjoys lower implementation complexity and reduced system overhead, which fully demonstrates that the proposed unequal secrecy protection scheme can realize a good performance-complexity tradeoff.

International Conference on Communications•May 1, 2018•1 citation

Securing Two-Way Cooperative Systems With an Untrusted Relay: A Constellation-Rotation Aided Approach

Hongbin Xu, Li Sun, Pinyi Ren +1 more

This letter studies the secure transmission protocol design for two-way cooperative systems, where two terminal users communicate via an untrusted relay. The relay acts as both a helper and a potential eavesdropper, from which the users' messages need to be kept secret. A constellation-rotation aided approach is proposed to prevent the relay from decoding these messages. By rotating the signal constellation with a proper angle, the complex-valued symbol can be fully represented by its real component. Then, either user utilizes only one dimension of the signal to deliver its information, with the other dimension carrying the artificial noise (AN). In this manner, the received signal-to-interference-plus-noise ratio (SINR) at the relay is degraded due to the injection of AN, thereby increasing the difficulty of eavesdropping. Moreover, the desired signal and the AN lie in different directions at the terminal users, which makes the signal detection free-of-interference. The approximate expression for the upper bound of the users' symbol error rate (SER) is derived based on which a criterion is developed to choose the rotation angle that can optimize the system SER performance. Simulation results demonstrate the superiority of our scheme compared to the competing candidates.

IEEE Communications Letters•Sep 16, 2015•29 citations

Constellation Superposition and Artificial Noise Against Interior and Exterior Eavesdropping in Bidirectional Untrusted Relaying Systems

Jiawei Zhao, Hongliang He, Nengcheng Chen

Untrusted bidirectional relay systems confront both internal and external eavesdropping problems, but existing studies generally focus on only one of them. This letter proposes a new scheme combining constellation superposition and artificial noise to resist both. First, we exploit constellation superposition to cause aliasing of the constellations at the untrusted relay to prevent its decoding. Then, we embed carefully designed artificial noise in the transmitted signal, making it difficult for an external eavesdropper to remove. Theoretical analysis and simulations verify that the proposed scheme maintains a high bit error rate for the untrusted relay while ensuring a lower bound of bit error rate for the external eavesdropper. In contrast, the bit error rate of the legitimate users decreases as the signal-to-noise ratio (SNR) at the transmitter increases.

IEEE Wireless Communications Letters•Oct 23, 2024•2 citations
This letter proposes a key exchange scheme for the untrusted relay system, where the relay not only assists in message transmission but also tries to recover messages. Terminal users initiate the process by transmitting a local key and utilize constellation overlapping techniques to create an overlapped constellation at the relay nodes, which increases the decoding error rate for relay eavesdropping but still poses a risk of key leakage. To address this, we propose a fine-grained entropy extraction algorithm that quantifies the overlapped constellation points into key bits, which are uniformly random bits from the relay’s perspective. In the constellation overlapping scenario, we can estimate the number of instances where the relay cannot distinguish. Leveraging this, our algorithm achieves remarkable levels of entropy utilization. QPSK enables perfect lossless entropy extraction, while other QAM modulation schemes can achieve a utilization rate of up to 96%.
This paper proposes a constellation overlapping scheme to secure two-way untrusted relaying systems, where the relay acts as both a helper facilitating data transmission and an eavesdropper intercepting users' messages. A truncated-channel-inversion based approach is developed to make the signals transmitted from two users experience the same equivalent channel, thereby realizing full constellation overlapping at the relay. Consequently, it is extremely difficult for the relay to recover the users' individual signals, and data confidentiality is thus protected. The achieved error floor level at the untrusted relay is analyzed, and the truncation thresholds are optimized to maximize the sum rate for end-to-end information exchange. Simulation results demonstrate the superiority of our scheme in terms of security and transmission efficiency compared with the existing alternatives.
This paper studies the secure information exchange of two-way relaying systems, where two terminal users communicate bi-directionally with the assistance of an untrusted relay. Each user is assumed to have two messages with distinct priorities: high priority and low priority. The high-priority messages (HPM) are first transmitted, for which we propose a constellation overlapping scheme such that the received signals at the relay overlap with each other and a high error floor is created to prevent the untrusted relay from deciphering the information. Upon the completion of HPM exchange, each user sends its low-priority message (LPM) by superposing it onto the previously decoded HPM from the other user. By exploiting the difference between the error patterns for HPM at the terminal users and the relay, channel noises in various time slots can be aggregated at the relay to secure the LPM transmission. The symbol error probability (SEP) at the terminal users as well as the untrusted relay is analyzed, from which it is shown that HPM is guaranteed to have greater reliability and higher secrecy level than that of LPM. However, the transmission of LPM enjoys lower implementation complexity and reduced system overhead, which fully demonstrates that the message-prioritization-based unequal secrecy protection framework can realize a good performance-complexity tradeoff. Simulation results exhibit the superiority of the proposed design compared to the existing competing solutions.
This paper proposes a novel technique called constellation overlapping to secure two-way untrusted relaying systems. We first consider the symmetric case where two terminal users adopt the same modulation type. For this case, a truncated-channel-inversion-based approach is developed to make the signals from different users experience the same equivalent channel, thereby realizing full constellation overlapping at the relay. Consequently, an error floor is created at the untrusted relay, and data confidentiality is protected. Then, the asymmetric case is investigated, where different modulations are employed at the two users and the constellation overlapping cannot be realized. To address this issue, we develop a constellation virtualization method, which exploits the intrinsic user-cooperation mechanism to “virtualize” two identical constellations at the two users. In this manner, the constellation overlapping effect can still be achieved, without sacrificing much reliability performance. We optimize the truncation threshold to maximize the sum rate for end-to-end information exchange, and design the bit-to-symbol mapping criterion and the signal detection method as well. Unlike the existing physical layer security approaches that guarantee secrecy with additional resource consumptions, this method realizes security enhancement by letting different users mutually encrypt their signals over the air, which is more resource-efficient.
This paper proposes a message-prioritization based unequal secrecy protection framework for untrusted two- way relaying networks, where two terminal users communicate bidirectionally with the assistance of an untrusted relay. Each user is assumed to have two messages with distinct priorities: high priority and low priority. The high priority messages (HPM) are first transmitted, for which we devise a constellation overlapping method such that the received signals at the relay overlap with each other and a high error floor is created to prevent the untrusted relay from deciphering the information. Upon the completion of HPM exchange, users transmit their low priority messages (LPM) using a noise aggregation approach. To be specific, each user superposes its LPM onto the previously decoded HPM from the other user. By exploiting the difference between the error patterns for HPM at the terminal users and the relay, channel noises in various time slots can be aggregated at the relay to secure the LPM transmission. It is shown from simulation results that HPM is guaranteed to have greater reliability and higher secrecy level than that of LPM. However, the transmission of LPM enjoys lower implementation complexity and reduced system overhead, which fully demonstrates that the proposed unequal secrecy protection scheme can realize a good performance-complexity tradeoff.
This letter studies the secure transmission protocol design for two-way cooperative systems, where two terminal users communicate via an untrusted relay. The relay acts as both a helper and a potential eavesdropper, from which the users' messages need to be kept secret. A constellation-rotation aided approach is proposed to prevent the relay from decoding these messages. By rotating the signal constellation with a proper angle, the complex-valued symbol can be fully represented by its real component. Then, either user utilizes only one dimension of the signal to deliver its information, with the other dimension carrying the artificial noise (AN). In this manner, the received signal-to-interference-plus-noise ratio (SINR) at the relay is degraded due to the injection of AN, thereby increasing the difficulty of eavesdropping. Moreover, the desired signal and the AN lie in different directions at the terminal users, which makes the signal detection free-of-interference. The approximate expression for the upper bound of the users' symbol error rate (SER) is derived based on which a criterion is developed to choose the rotation angle that can optimize the system SER performance. Simulation results demonstrate the superiority of our scheme compared to the competing candidates.
Untrusted bidirectional relay systems confront both internal and external eavesdropping problems, but existing studies generally focus on only one of them. This letter proposes a new scheme combining constellation superposition and artificial noise to resist both. First, we exploit constellation superposition to cause aliasing of the constellations at the untrusted relay to prevent its decoding. Then, we embed carefully designed artificial noise in the transmitted signal, making it difficult for an external eavesdropper to remove. Theoretical analysis and simulations verify that the proposed scheme maintains a high bit error rate for the untrusted relay while ensuring a lower bound of bit error rate for the external eavesdropper. In contrast, the bit error rate of the legitimate users decreases as the signal-to-noise ratio (SNR) at the transmitter increases.