We consider secret key agreement based on radio propagation characteristics in two-way relaying system where two legitimate parties named Alice and Bob communicate with each other via a relay. In this system, Alice and Bob share secret keys generated from their radio propagation characteristics by the help of the relay. In this paper, we present two secret key agreement schemes: an amplify-and-forward (AF) scheme and a multiple-access amplify-and-forward (MA-AF) scheme. In both of the schemes, the basic idea is to share the effective fading coefficient between Alice and Bob and use it as the source of secret keys. The AF scheme is based on a conventional amplify-and-forward two-way relaying method, while the MA-AF scheme utilizes the inherent combining of signals provided by simultaneous transmissions over a multiple-access channel in order to share the secret keys more securely efficiently. We analyze eavesdropping strategy in terms of eavesdropper's location and show that if the eavesdropper is located near the relay and can receive signals from the relay without multipath fading and noise, the AF scheme is not secure. Simulation results show that the MA-AF scheme is more secure and efficient than the AF scheme.
We consider secret key agreement based on radio propagation characteristics in two-way relaying system where two legitimate parties named Alice and Bob communicate with each other via a relay. In this system, Alice and Bob share secret keys generated from their radio propagation characteristics by the help of the relay. In this paper, we present two secret key agreement schemes: an amplify-and-forward (AF) scheme and a multiple-access amplify-and-forward (MA-AF) scheme. In both of the schemes, the basic idea is to share the effective fading coefficient between Alice and Bob and use it as the source of secret keys. The AF scheme is based on a conventional amplify-and-forward two-way relaying method, while the MA-AF scheme utilizes the inherent combining of signals provided by simultaneous transmissions over a multiple-access channel in order to share the secret keys more securely efficiently. We analyze eavesdropping strategy in terms of eavesdropper's location and show that if the eavesdropper is located near the relay and can receive signals from the relay without multipath fading and noise, the AF scheme is not secure. Simulation results show that the MA-AF scheme is more secure and efficient than the AF scheme.
We consider secret key agreement based on radio propagation characteristics in a two-way relaying system where two legitimate parties named Alice and Bob communicate with each other via a trusted relay. In this system, Alice and Bob share secret keys generated from measured radio propagation characteristics with the help of the relay in the presence of an eavesdropper. We present four secret key agreement schemes: an amplify-and-forward (AF) scheme, a signal-combining amplify-and-forward (SC-AF) scheme, a multiple-access amplify-and-forward (MA-AF) scheme, and an amplify-and-forward with artificial noise (AF with AN) scheme. In these schemes, the basic idea is to share the effective fading coefficients between Alice and Bob and use them as the source of the secret keys. The AF scheme is based on a conventional amplify-and-forward two-way relaying method, whereas in the SC-AF scheme and the MA-AF scheme, we apply the idea of physical-layer network coding to the secret key agreement. In the AF with AN scheme, the relay transmits artificially generated noise, as well as channel information signal, in order to conceal the latter. Simulation results show that the MA-AF scheme outperforms the other schemes in Rayleigh fading channels, whereas the AF with AN scheme is suitable for Rician fading channels.
We consider secret key agreement for multiple terminals based on radio propagation characteristics in a wireless relaying system where more than two terminals communicate with each other via a relay. In this system, the multiple terminals share a common secret key generated from their radio propagation characteristics with the help of the relay in the presence of an eavesdropper. In this paper, we present three secret key agreement schemes: an amplify-and-forward (AF) scheme, a signal-combining amplify-and-forward (SC-AF) scheme, and a multiple-access amplify-and-forward (MA-AF) scheme. The key idea of these schemes is that each terminal shares the fading coefficients between all terminals and the relay, and use them as the source of a secret key. The AF scheme is based on a conventional amplify-and-forward two-way relaying method, whereas in the SC-AF scheme and the MA-AF scheme, we apply the idea of analog network coding to secret key agreement. We analyze eavesdropping strategies and show that the AF scheme is not secure if the eavesdropper is located near the relay and can receive signals from the relay without multipath fading and noise. Simulation results show that the SC-AF and MA-AF schemes are effective.
In this work, information security of a cooperative wireless communication system over three-phase amplify-and-forward (AF) two-way relaying channels is investigated. A relay power allocation scheme is proposed to improve secrecy capacity of the system. We first derive the secrecy rate expression for the basic scenario which consists of one source, one destination, one single relay, and an eavesdropper. A relay power allocation scheme which maximizes the overall secrecy rate of the single-relay system is studied accordingly. Then the power allocation coefficients are calculated under the assumption of perfect channel state information (CSI). This design framework is then extended to a cooperative wireless system having multiple relays. In the numerical example, secrecy rate performance of the proposed scheme is compared with the classic three-phase two-way AF scheme and it is concluded that conducting power allocation at the relay can achieve the goal of improving the secrecy capacity. It is also observed that the best performing scenario of the relay power allocation scheme is when the relay locates right in the middle of the two legitimate communicants.
In this paper, we consider the two-way relay network (TWRN) in the presence of an eavesdropper, and construct a noisy amplify-and-forward (AF) algorithm to enhance the physical (PHY) layer security capacity. All the source nodes, the relay and the eavesdropper are equipped with multiple antennas. In the proposed noisy AF scheme, the relay first receives signals from both source nodes, adds weighted artificial noise (AN), and then amplifies and forwards the modified signal to both source nodes. In this scenario, we analyze the effects of AN and the number of relay antennas on the secrecy sum rate for different conditioning channel matrices. It is shown that AN will result in an increased secrecy sum rate, and the channel condition is a key parameter of the system in deciding the sum secrecy rate. Finally, simulation results demonstrate the validity of proposed studies.
In this paper, we investigate security issues in a collaborative wireless network in the presence of eavesdropping attacks, where multiple amplify-and-forward (AF) relays are exploited to secure the message transmission between legitimate users. We first consider the multiple AF relays all participating in assisting the transmission from source to destination, which is called all-relay based collaborative transmission scheme as denoted by all-relay scheme for notational convenience. We also propose the best-relay transmission scheme in which only the single “best” relay is selected to help the source transmit messages to destination. We then analyze the intercept behavior in wireless networks and evaluate intercept probabilities of the proposed all-relay and best-relay schemes as well as the conventional direct transmission without relay in a Rayleigh fading environment. Numerical results show that the best-relay transmission scheme always outperforms the all-relay and direct transmission schemes in terms of intercept probability. It is also shown that as the number of eavesdroppers increases, the intercept probabilities of both all-relay and best-relay schemes increase. Moreover, the intercept probability performance of all-relay and best-relay schemes significantly improves with an increasing number of relays, implying the advantage of exploiting multiple relays against eavesdropping attacks.
The communication process of a secure relay system usually has two stages: source to relay, relay to destination. When the source is only equipped with one antenna, the information transmission is not secure during the first stage. In this paper, we propose a novel three-stage scheme to transmit confidential messages in an amplify-and-forward (AF) relay system. In the proposal, during the additional stage all the relays independently send artificial interference signals to the source. Then in the next stage, the sending signals of the source node are mixed with both the confidential messages and the interference signals received in the first stage. Finally the relays forward the hybrid signals to the destination node, and cancel the interference signals simultaneously. Since the sending signals are hybrid, all the three stages are secure in the proposed scheme, even when the eavesdropper is located very close to the source, positive secrecy rate of the system can still be achieved. Simulation results verify that the proposed scheme has much better near-field performance than the traditional secure relay communication schemes.