This paper investigates the achievable secrecy regions when employing a friendly jammer in a cooperative scenario employing an untrusted relay. The untrusted relay which helps to forward the source signal towards the destination, could also be regarded as a potential eavesdropper. Our system employs a friendly jammer which sends a known noise signal towards the relay. In this paper, we investigate the effect of jammer and relay locations on the achievable secrecy rate. We consider two scenarios where in the first case we consider no direct transmission between the source and destination, while in the second case we include a source to destination direct link in our communication system.
This paper investigates the achievable secrecy regions when employing a friendly jammer in a cooperative scenario employing an untrusted relay. The untrusted relay which helps to forward the source signal towards the destination, could also be regarded as a potential eavesdropper. Our system employs a friendly jammer which sends a known noise signal towards the relay. In this paper, we investigate the effect of jammer and relay locations on the achievable secrecy rate. We consider two scenarios where in the first case we consider no direct transmission between the source and destination, while in the second case we include a source to destination direct link in our communication system.
In this paper, we consider a two-way relay system where the two sources can only communicate through an untrusted intermediate relay and investigate the physical layer security issue in this two-way untrusted relay scenario. Specifically, we regard the intermediate relay as an eavesdropper from which the information transmitted by the sources needs to be kept confidential, despite the fact that its cooperation in relaying this information is essential. We first indicate that a nonzero secrecy rate is indeed achievable in this two-way untrusted relay system even without the help of external friendly jammers. As for the system with friendly jammers, after further analysis, we can obtain the secrecy rate of the sources can be effectively improved by utilizing proper jamming power from the friendly jammers. Then, we formulate a Stackelberg game between the sources and the friendly jammers as a power control scheme to achieve the optimized secrecy rate of the sources, in which the sources are treated as the sole buyer and the friendly jammers are the sellers. In addition, the optimal solutions of the jamming power and the asking prices are given, and a distributed updating algorithm to obtain the Stackelberg equilibrium is provided for the proposed game. Finally, the simulation results verify the properties and efficiency of the proposed Stackelberg-game-based scheme.
In this paper, we consider a two-way relay network where two sources can communicate only through an unauthenticated intermediate relay node. We investigate secure communications of this two-way relay scenario using physical layer security. Specifically, we treat the relay node as an eavesdropper from whom the information transmitted by the sources needs to be kept secret, despite the fact that its cooperation in relaying this information is essential. We first find that a non-zero secrecy rate is indeed achievable in this two-way relay network even without external jammers. Further still, with the help of friendly jammers who can transmit jamming signals to distract the malicious relay, a positive gain of the secrecy rate can be realized. In order to obtain the maximum secrecy rate, we define and then analyze an optimization problem. Finally, an optimal solution of jamming power allocation is provided for the system with friendly jammers.
We consider a source-destination pair that can communicate only through an unauthenticated intermediate relay node. In this two-hop communication scenario, where the cooperation from the relay node is essential, we investigate whether achieving non-zero secrecy rate is possible. Specifically, we treat the relay node as an eavesdropper from whom the source information needs to be kept secret, despite the fact that its cooperation in relaying this information is needed. We find that a positive secrecy rate is indeed achievable, with the aid of the destination node or an external node that jams the relay, i.e., by cooperative jamming. We derive an upper bound on the secrecy rate by means of an eavesdropper-relay separation argument. We remark that this upper bound is the first of its kind in Gaussian channels with cooperative jamming. The upper bound is strictly smaller than the channel capacity without secrecy constraints. The achievable secrecy rates are found using stochastic encoding and compress-and-forward at the relay. Numerical results show that the gap between the bound and the achievable rate is small when the relay's power is larger than the power of the jammer and the source. In essence, this paper shows that a cooperative jammer enables secure communication to take place using an untrusted relay which would be otherwise impossible.
We consider the communication scenario where a source-destination pair wishes to keep the information secret from a relay node despite wanting to enlist its help. For this scenario, an interesting question is whether the relay node should be deployed at all. That is, whether cooperation with an untrusted relay node can ever be beneficial. We first provide an achievable secrecy rate for the general untrusted relay channel, and proceed to investigate this question for two types of relay networks with orthogonal components. For the first model, there is an orthogonal link from the source to the relay. For the second model, there is an orthogonal link from the relay to the destination. For the first model, we find the equivocation capacity region and show that answer is negative. In contrast, for the second model, we find that the answer is positive. Specifically, we show, by means of the achievable secrecy rate based on compress-and-forward, that by asking the untrusted relay node to relay information, we can achieve a higher secrecy rate than just treating the relay as an eavesdropper. For a special class of the second model, where the relay is not interfering itself, we derive an upper bound for the secrecy rate using an argument whose net effect is to separate the eavesdropper from the relay. The merit of the new upper bound is demonstrated on two channels that belong to this special class. The Gaussian case of the second model mentioned above benefits from this approach in that the new upper bound improves the previously known bounds. For the Cover-Kim deterministic relay channel, the new upper bound finds the secrecy capacity when the source-destination link is not worse than the source-relay link, by matching with achievable rate we present.
To improve physical (PHY) layer security of a wireless relay system in the presence of an eavesdropper, a two-phase cooperative relaying scheme is investigated in this paper. In phase I, the source transmits confidential message, simultaneously, it cooperates with the friendly jammers and destination to create jamming signal at the eavesdropper without affecting the forwarding relay which is preselected. In phase II, the forwarding relay retransmits the decoded signal, meanwhile, the particular relay cooperates with the friendly jammers to create jamming signal at the eavesdropper without affecting the destination. We focus on the investigation of optimal power allocation for maximizing achievable secrecy rate subject to a total power constraint. Optimal relay selection and suboptimal relay selection schemes are also proposed. It is shown that as the number of relays increases, both secrecy rate and the performance of suboptimal relay selection scheme improve significantly. Numerical results are presented to validate the derived analytical results and compare them to existing work.
This paper investigates a power control scheme for cooperative cognitive communication system which employs an untrusted relay. More explicitly, a friendly jammer transmits a jamming signal enabling secure communication between the source and the destination, in the presence of an untrusted relay. In return, the source compensates the potential jammer with an access to its bandwidth for a fraction of its time period. In addition, cooperative jammer defines its jamming power through Nash-Equilibrium for improving the secrecy rate. In our proposed scheme, we employ only one jammer and place it on different locations in order to analyze the secrecy rate achieved and the utility of the jammer. Additionally, we fix the positions of the source and the destination while the relay is moved at different locations.