Physical layer authentication techniques developed in conventional macrocell wireless networks face challenges when applied in the future fifth-generation (5G) wireless communications, due to the deployment of dense small cells in a hierarchical network architecture. In this paper, we propose a novel physical layer authentication scheme by exploiting the advantages of amplify-and-forward (AF) cooperative relaying, which can increase the coverage and convergence of the heterogeneous networks. The essence of the proposed scheme is to select the best relay among multiple AF relays for cooperation between legitimate transmitter and intended receiver in the presence of a spoofer. To achieve this goal, two best relay selection schemes are developed by maximizing the signal-to-noise ratio (SNR) of the legitimate link to the spoofing link at the destination and relays, respectively. In the sequel, we derive closed-form expressions for the outage probabilities of the effective SNR ratios at the destination. With the help of the best relay, a new test statistic is developed for making an authentication decision, based on normalized channel difference between adjacent end-to-end channel estimates at the destination. The performance of the proposed authentication scheme is compared with that in a direct transmission in terms of outage and spoofing detection.

Location privacy preservation in multi-channel cognitive radio mobile ad hoc networks (CR-MANETs) is a challenging issue, where the network does not rely on a trusted central entity to impose privacy-preserving protocols. Furthermore, even though the multi-channel CR-MANETs have numerous advantages, utilization of multiple channels degrades the location privacy, by disclosing more information about CRs. In this paper, location privacy is studied for cooperative spectrum sensing (CSS) in multi-channel CR-MANETs.We first quantify the location privacy. Then, we propose a new privacy-preserving distributed cooperative spectrum sensing scheme for multi-channel CR-MANETs. We design a new anonymization method based on random manipulation of the exchanged signal-to-noise ratio (SNR). Afterwards, a coalitional game-theoretic distributed channel assignment is proposed to maximize location privacy and sensing performance over each channel in the network. Simulation results show that the proposed scheme can enhance sensing performance and location privacy over multiple channels.

The inherent properties of channel impulse response CIR, which are considered as location-specific characteristics of the physical link, have been exploited for the authentication purpose at the physical layer in the wireless communications. Unfortunately, the reliability of CIR-based physical layer authentication is challenged by the noise present in the CIR estimates, the rapid channel variation induced by the mobility of terminals, and the weak authentication decision by exploiting single CIR difference under the hypothesis testing. In this paper, three CIR-based authentication schemes are proposed to enhance the authentication reliability. Specifically, the noise components of the CIR estimates are mitigated in order to derive an adaptive threshold to form the authentication decision. Additionally, because of the rapid variation of the fading channel, channel prediction technique is employed to predict future CIR, and which is exploited to derive the CIR difference for the authentication analysis. Furthermore, to form the final decision in the authentication process, multiple CIR differences are observed by the receiver in a long range based on the channel predictor. In order to optimize the number of CIR differences, an optimization algorithm is developed by minimizing the total error rate under a false alarm constraint. Finally, the false alarm rate and the probability of detection are theoretically derived for performance evaluation, and the performance of proposed schemes is compared with that of a traditional channel-based authentication method using computer simulation. Copyright © 2014 John Wiley & Sons, Ltd.

Mobile Ad hoc NETworks (MANETs) are a promising communication technology for tactical environments and emergency response operations. However, the features of MANETs, including dynamic topology and open wireless medium, lead to many security vulnerabilities. Malicious nodes can drop or modify packets that are received from other nodes and diminish the reliability of networks. Therefore, secure routing in MANETs is an important area of research. In this paper, we propose a scheme that enhances routing security based on trust. In the proposed scheme, in order to improve the accuracy of trust values with indirect observations, we use Dempster-Shafer theory of evidence to fuse observers' opinions. Consequently, a more accurate trust value can be calculated from indirect observations. We then utilize the trust value to enhance the MANET routing protocol security. Simulation results are presented to demonstrate the effectiveness of the proposed scheme.

Game theory can provide a useful tool to study the security problem in mobile ad hoc networks (MANETs). Most of existing works on applying game theories to security only consider two players in the security game model: an attacker and a defender. While this assumption may be valid for a network with centralized administration, it is not realistic in MANETs, where centralized administration is not available. In this paper, using recent advances in mean field game theory, we propose a novel game theoretic approach with multiple players for security in MANETs. The mean field game theory provides a powerful mathematical tool for problems with a large number of players. The proposed scheme can enable an individual node in MANETs to make strategic security defence decisions without centralized administration. In addition, since security defence mechanisms consume precious system resources (e.g., energy), the proposed scheme considers not only the security requirement of MANETs but also the system resources. Moreover, each node in the proposed scheme only needs to know its own state information and the aggregate effect of the other nodes in the MANET. Therefore, the proposed scheme is a fully distributed scheme. Simulation results are presented to illustrate the effectiveness of the proposed scheme.

In cooperative wireless networks, relay nodes are employed to improve the performance of the network in terms of throughput and reliability. However, the presence of malicious relay nodes in the network may severely degrade the performance of the system. When a relay node behaves maliciously, there exists a possibility that such a node refuses to cooperate when it is selected for cooperation or deliberately drops the received packets. Trust establishment is a mechanism to detect misbehaving nodes in a network. In this paper, we propose a trust establishment method for cooperative wireless networks by using Bayesian framework. In contrast with the previous schemes proposed in wireless networks, this approach takes the channel state information and the relay selection decisions into account to derive a pure trust value for each relay node. The proposed method can be applied to any cooperative system with a general relay selection policy whose decisions in each cooperative transmission are independent of the previous ones. Moreover, it does not impose additional communication overhead on the system as it uses the available information in relay selection procedure. Copyright © 2012 John Wiley & Sons, Ltd.

Cognitive radios (CRs), which are capable of sensing its surrounding environment and adapting its internal parameters, have been considered in mobile ad hoc networks (MANETs). The area of security in CR-MANETs has received far less attention than other areas. However, some distinct characteristics of CRs introduce new non-trivial security risks to CR-MANETs. In this article, the authors study spectrum sensing data falsification (SSDF) attacks to CR-MANETs, in which intruders send false local spectrum sensing results in cooperative spectrum sensing, and it will result in wrong spectrum sensing decisions by CRs. The authors present a novel bio-inspired consensus-based cooperative spectrum sensing scheme to counter SSDF attacks in CR-MANETs. Their scheme is based on recent advances in consensus algorithms that have taken inspiration from self-organising behaviour of animal groups such as birds, fish, ants, honeybees and others. Unlike the existing schemes, there is no need for a common receiver to do the data fusion for reaching the final decision to counter SSDF attacks. The scheme has self-configuration and self-maintenance capabilities. Moreover, in order to further improve the security of CR-MANETs, the authors present an authentication scheme using identity (ID)-based cryptography with threshold secret sharing. Simulation results are presented to show the effectiveness of the proposed schemes.

In this survey, we present a comprehensive list of major known security threats within a cognitive radio network (CRN) framework. We classify attack techniques based on the type of attacker, namely exogenous (external) attackers, intruding malicious nodes and greedy cognitive radios (CRs). We further discuss threats related to infrastructure-based CRNs as well as infrastructure-less networks. Besides the short-term effects of attacks over CRN performance, we also discuss the often ignored longer term behavioral changes that are enforced by such attacks via the learning capability of CRN. After elaborating on various attack strategies, we discuss potential solutions to combat those attacks. An overview of robust CR communications is also presented. We finally elaborate on future research directions pertinent to CRN security. We hope this survey paper can provide the insight and the roadmap for future research efforts in the emerging field of CRN security.

Continuous authentication is an important prevention-based approach to protect high security mobile ad-hoc networks (MANETs). On the other hand, intrusion detection systems (IDSs) are also important in MANETs to effectively identify malicious activities. Considering these two approaches jointly is effective in optimal security design taking into account system security requirements and resource constraints in MANETs. To obtain the optimal scheme of combining continuous authentication and IDSs in a distributed manner, we formulate the problem as a partially observable distributed stochastic system. We present structural results for this problem in order to decrease computational complexity, making our solution usable in large networks. The policies derived from structural results are easy to implement in practical MANETs. Simulation results are presented to show the performance of this method for the proposed scheme.

Traditional authentication techniques for wireless communications are facing great challenges, due to the open radio propagation environment and limited options of transmission techniques. A new continuous physical layer authentication technique with time-varying transmission parameters is investigated to enhance the security of orthogonal frequency division multiplexing (OFDM) system. A preceded cyclic prefix (PCP) sequence, which introduces an additional signaling link to carry the time-varying transmission parameters, is employed in each OFDM symbol for physical layer authentication. The new PCP sequences are generated with the same time and frequency domain characteristics as data-carrying OFDM signals to reduce the interception probability. With the proper recovery of system parameters and interference cancellation, only legitimate users can successfully decode the PCP sequence and obtain necessary parameters to decode OFDM data. In addition, a cross layer design approach, which addresses the dependency among PCP configurations, authentication performance and transmitting performance, is introduced to continuously generate optimal PCPs according to dynamic communication conditions. Numerical simulations confirmed that the system performance, in terms of system robustness, security and stealth, can be significantly improved by using the proposed continuous authentication.

Continuous user authentication is an important prevention-based approach to protect high security mobile ad-hoc networks (MANETs). On the other hand, intrusion detection systems (IDSs) are also important in MANETs to effectively identify malicious activities. Considering these two approaches jointly is effective in optimal security design taking into account system security requirements and resource constraints in MANETs. To obtain the optimal scheme of combining continuous user authentication and IDSs in a distributed manner, we formulate the problem as a partially observable Markov decision process (POMDP) multi-armed bandit problem. We present a structural results method to solve the problem for a large network with a variety of nodes. The policies derived from structural results are easy to implement in practical MANETs. Simulation results are presented to show the effectiveness and the performance of the proposed scheme.

Cooperative communication makes use of the broadcast nature of the wireless medium where adjacent nodes overhear the message transmitted by the source and assist in the transmission by relaying the overheard message to the destination. Although cooperative communication brings in significant benefits, it also raises serious security issues to wireless mobile networks. For example, there exists a possibility that a node refuses to cooperate when it is selected for cooperation or deliberately drop the received packets. In wireless mobile networks with cooperative communication, trust management is an important mechanism to monitor such networks for violations of security. In this paper, we propose a trust management method for wireless mobile networks with cooperative communications. Conventional Bayesian methodology is insufficient for the cooperative communication paradigm, as it is biased by the channel conditions and relay selection decision processes. Therefore, we modify the conventional trust management method by incorporating not only the relay selection policy but also the dynamic wireless channel conditions among the source, relays and destination. Simulation results are presented to show the effectiveness of the proposed scheme.

Cooperative communication is considered a promising technique to increase channel capacity and improve reliability in wireless and cellular networks. However, it also raises a number of serious security issues as malicious nodes may impersonate and affect the integrity of the communication. In this paper, we propose a prevention-based security technique for cooperative communication taking into consideration authentication protocol, based on hash chains and Merkle trees, along with physical layer parameters which relate to the channel state information. Based on this consideration, we derive the closed-form secured throughput equations for proactive relay selection in cooperative communication that provides both hop-by-hop and end-to-end authentication and integrity protection. The simulation results show that our proposed solution, which provides authentication and protects data integrity, has a higher throughput performance when compared to existing schemes that do not consider security.

Hierarchical key management schemes would serve well for military applications where the organization of the network is already hierarchical in nature. Most of the existing key management schemes concentrate only on network structures and key allocation algorithms, ignoring attributes of the nodes themselves. Due to the distributed and dynamic nature of MANETs, it is possible to show that there is a security benefit to be attained when the node states are considered in the process of constructing a private key generator (PKG). In this paper, we propose a distributed hierarchical key management scheme in which nodes can get their keys updated either from their parent nodes or a threshold of sibling nodes. The dynamic node selection process is formulated as a stochastic problem and the proposed scheme can select the best nodes to be used as PKGs from all available ones considering their security conditions and energy states. Simulation results show that the proposed scheme can decrease network compromising probability and increase network lifetime in tactical MANETs.

Efficient communications are crucial for disaster response and recovery. However, most current public safety land mobile radio (LMR) networks only provide narrowband voice service with limited support of low-speed data services. In this paper, we study to enhance the interoperability of LMR with commercial wireless cellular networks, by which a wide variety of benefits can be offered to disaster responders, including new multimedia services, increased data rates and low cost devices. Our approach is based on Session Initiation Protocol (SIP) and a joint radio resource management framework. We use a novel SIP- based seamless handoff scheme to support the interoperability between cellular and LMR networks. In addition, an optimal radio resource management scheme is proposed to maximize the overall radio resource utilization and at the same time guarantee service availability and continuity quality of service (QoS) for disaster responders. The effectiveness of the proposed schemes is illustrated by numerical examples.

Two complementary classes of approaches exist to protect high security mobile ad hoc networks (MANETs), prevention-based approaches, such as authentication, and detection-based approaches, such as intrusion detection. Most previous work studies these two classes of issues separately. In this paper, we propose a framework of combining intrusion detection and continuous authentication in MANETs. In this framework, multimodal biometrics are used for continuous authentication, and intrusion detection is modeled as sensors to detect system security state. We formulate the whole system as a partially observed Markov decision process considering both system security requirements and resource constraints. We then use dynamic programming-based hidden Markov model scheduling algorithms to derive the optimal schemes for both intrusion detection and continuous authentication. Extensive simulations show the effectiveness of the proposed scheme.

Two complementary classes of approaches exist to protect high security mobile ad hoc networks (MANETs), prevention-based approaches, such as authentication, and detection-based approaches, such as intrusion detection. Most previous work studies these two classes of issues separately. In this paper, we propose a framework of combining intrusion detection and continuous authentication in MANETs. In this framework, multimodal biometrics are used for continuous authentication, and intrusion detection is modeled as sensors to detect system security state. We formulate the system and use dynamic programming- based algorithms to derive the optimal schemes for both intrusion detection and continuous authentication. Simulation examples show the effectiveness of the proposed scheme.

Abstract As the front line of defense, user authentication is crucial for integrity and confidentiality. Mobile ad hoc networks (MANETs) impose a number of non‐trivial challenges to user authentication such as lack of central coordination and limited resources. In high security MANETs, continuous authentication is desirable so that a system can be monitored for the duration of the session to reduce the vulnerability. Biometrics provides some possible solutions to the authentication problem in MANETs, since it has direct connection with user identity. In this paper, we introduce some biometric technologies and their applications in the authentication problem. Multimodal biometrics can be used to exploit the benefits of one biometric while mitigating the inaccuracies of another. We propose an optimal multimodal biometric‐based continuous authentication scheme in MANETs. Some numerical results show the effectiveness of the proposed scheme. Copyright © 2007 John Wiley & Sons, Ltd.

The complementary characteristics of public safety radio networks and commercial cellular networks make it attractive to integrate these two wireless access technologies to provide first responders with a wide variety of advanced services (e.g., multimedia). In this integrated system, service availability is a critical quality of service (QoS) requirement. This paper formulates the QoS provisioning problem and proposes an algorithm for solving the problem. The QoS constraint can be guaranteed in the proposed scheme by reserving some bandwidth in cellular networks for first responders. Numerical examples illustrate that the proposed scheme can significantly improve the service availability QoS for first responders.