The use of multiple network configurations for cooperative jamming with the aim to increase the region with information-theoretic secrecy is analysed. The case with a single eavesdropper at an unknown location is investigated. A pre-master key message is broken into multiple data blocks, which are then sent for different network configurations. Provided that the secrecy capacity for a given eavesdropper's position is positive for at least one configuration, the corresponding data block can be securely delivered to the receiver, and thus the eavesdropper can not discover the master key.
The use of multiple network configurations for cooperative jamming with the aim to increase the region with information-theoretic secrecy is analysed. The case with a single eavesdropper at an unknown location is investigated. A pre-master key message is broken into multiple data blocks, which are then sent for different network configurations. Provided that the secrecy capacity for a given eavesdropper's position is positive for at least one configuration, the corresponding data block can be securely delivered to the receiver, and thus the eavesdropper can not discover the master key.
Consider a one-dimensional wireless network with n nodes uniformly and independently distributed at random in the interval. In addition, m eavesdropper nodes are uniformly and independently distributed in. For a randomly selected source-destination pair, we consider the problem of securely delivering a message from the source to the destination and we present achievable results on the number of eavesdropper nodes that can be tolerated by the network. Our constructions make use of cooperative jamming, in which nodes located close to the eavesdroppers generate artificial noise. For the one-dimensional network case, our results provide an improvement to the connectivity properties of the recently-introduced secrecy graph which is disconnected for any positive number of eavesdroppers without cooperative jamming. We consider cases of both known and unknown eavesdropper locations. For known eavesdropper locations, we show that a message can be securely delivered from the source to the destination with probability one as the number of nodes n goes to infinity, for any number of independent eavesdroppers m(n) satisfying m(n) = o(√n / log n). For unknown eavesdropper locations, we present a construction which can tolerate m(n) = o(n/log n) under the assumption of independent eavesdroppers, but which is fragile in the face of collaborating eavesdroppers.
Information-theoretic secrecy is combined with cryptographic secrecy to create a secret-key exchange protocol for wireless networks. A network of transmitters, which already have cryptographically secured channels between them, cooperate to exchange a secret key with a new receiver at a random location, in the presence of passive eavesdroppers at unknown locations. Two spatial point processes, homogeneous Poisson process and independent uniformly distributed points, are used for the spatial distributions of transmitters and eavesdroppers. We analyse the impact of the number of cooperating transmitters and the number of eavesdroppers on the area fraction where secure communication is possible. Upper bounds on the probability of existence of positive secrecy between the cooperating transmitters and the receiver are derived. The closeness of the upper bounds to the real value is then estimated by means of numerical simulations. Simulations also indicate that a deterministic spatial distribution for the transmitters, for example, hexagonal and square lattices, increases the probability of existence of positive secrecy capacity compared to the random spatial distributions. For the same number of friendly nodes, cooperative transmitting provides a dramatically larger secrecy region than cooperative jamming and cooperative relaying.
In this paper, we investigate cooperative security in wireless networks, where a source (Alice) intends to transmit a confidential message to a legitimate destination (Bob), with the help of a cooperative node (Charlie), in the presence of multiple independent eavesdroppers (Eves). In particular, cooperative jamming (CJ) is explored to enhance secure communication between Alice and Bob. We provide a transmit design to maximize the secrecy rate, subject to a secrecy outage probability (SOP) constraint. Specifically, we establish a condition under which positive secrecy rate can be guaranteed. In addition to secrecy rate performance, we also pay attention to the secure energy efficiency, defined as the ratio of secrecy rate to total power consumption. Numerical results validate the effectiveness and energy efficiency of our proposed CJ scheme.
Physical layer secrecy in wireless networks in the presence of eavesdroppers of unknown location is considered. In contrast to prior schemes, which have expended energy in the form of cooperative jamming to enable secrecy, we develop schemes where multiple transmitters send their signals in a cooperative fashion to confuse the eavesdroppers. Hence, power is not expended on “artificial noise”; rather, the signal of a given transmitter is protected by the aggregate interference produced by the other transmitters. We introduce a two-hop strategy for the case of equal path-loss between all pairs of nodes, and then consider its embedding within a multi-hop approach for the general case of an extended network. In each case, we derive an achievable number of eavesdroppers that can be present in the region while secure communication between all sources and intended destinations is ensured.
A cooperative jamming system is investigated to enhance security of wireless communications in the presence of eavesdroppers. Different from traditional wireless security strategies that maximize secrecy capacity, a novel strategy based on the minimization of compromised secrecy region (CSR) is proposed. The secrecy region with a given secrecy outage probability is derived by considering path-loss and fading channel effects. Through numerical approximation of the outage probability, the optimal location and allocated power of the jammer are calculated to minimize the CSR which exhibits high secrecy outage probability. Without knowing the exact location of the randomly-distributed eavesdropper, our proposed scheme provides a new optimization criterion based on this compromised area minimization, thereby increasing the security level in cooperative jamming systems. Numerical results further validate the proposed CSR minimization scheme for cooperative jamming.
The growth of wireless networks has been considerable over the last decades. Due to the broadcast nature of these networks, security issues have taken a critical role in today’s communications. A promising direction towards achieving secure communications is information theoretic secrecy, which is an approach exploiting the randomness of the channels to ensure secrecy. Based on this approach, there has been a recent surge of interest in a potential cooperation between users to enhance the secrecy of communications. In this thesis we investigate the interaction between cooperation and secrecy. In particular the contributions of the thesis can be divided into two parts. In the first part, we study cooperative strategies for secrecy for wireless channels. Our goal is to evaluate the effect of fading and limited CSI on the eavesdropper’s channels. In that purpose we consider a scenario where a helper aims at increasing the secrecy of the communication between a source and destination in the presence of an eavesdropper. Several strategies are discussed for the helper, namely decode-and-forward, amplify-and-forward, and cooperative jamming. We introduce the secrecy outage probability, the conditional secrecy outage probability and the secure throughput as secrecy measures. For each measure, we investigate and compare the secrecy performance of cooperation. We furthermore elaborate a system optimization in terms of strategy selection, node positioning, power allocation and rate design. In the second part, we consider cooperation in the 4-node scenario against a more sophisticated adversary: an active eavesdropper, which can either passively eavesdrop, or jam the transmission. A game-theoretic perspective is a natural way to analyze the competitive interaction between the helper and the eavesdropper. Therefore we define several secrecy games, for which we find the Nash and Stackelberg equilibria as well as the corresponding secrecy rate outcomes. Another important consideration in this scenario is the interaction between the source and the helper, which we model and solve as a Stackelberg game, and we illustrate its impact on the achievable secrecy rates.