In this paper, we propose a secure transmission protocol for two users exchanging their respective information in an n-hop MIMO Ad hoc network. By exploiting the properties of the transmission medium in the physical layer, three channel models are utilized to provide secure transmission, namely one-way relay channel, two-way untrusted relay channel, and multiple access channel. Using these channel models, we design a basic protocol with a minimized time slot cost, i.e. n+1. Based on this basic protocol, we show that the attacker, either untrusted relay or external eavesdropper, can only obtain a summed signal in each time slot, and this summed signal cannot be decomposed to recover the individual information from the users. We then present cryptographic analysis for the first time to identify a weakness which is common for all known security schemes based on the summed signal. Thirdly, we introduce an evolutionary protocol proposed with two rounds of interlaced information exchange, which defeats this weakness. Finally, the simulation is performed to demonstrate the theoretical analysis.
In this paper, we propose a secure transmission protocol for two users exchanging their respective information in an n-hop MIMO Ad hoc network. By exploiting the properties of the transmission medium in the physical layer, three channel models are utilized to provide secure transmission, namely one-way relay channel, two-way untrusted relay channel, and multiple access channel. Using these channel models, we design a basic protocol with a minimized time slot cost, i.e. n+1. Based on this basic protocol, we show that the attacker, either untrusted relay or external eavesdropper, can only obtain a summed signal in each time slot, and this summed signal cannot be decomposed to recover the individual information from the users. We then present cryptographic analysis for the first time to identify a weakness which is common for all known security schemes based on the summed signal. Thirdly, we introduce an evolutionary protocol proposed with two rounds of interlaced information exchange, which defeats this weakness. Finally, the simulation is performed to demonstrate the theoretical analysis.
In this paper, we propose a novel secure transmission scheme for multiple-input multiple- output (MIMO) Two-Way relay channels, where multi- pair communication partners exchange information securely with the help of relay. By utilizing the properties of transmission medium in physical layer, our scheme can achieve high transmission efficiency as well as information theoretic security. With the secrecy capacity analysis, we show that our scheme is a secure approach under two different adversarial models: 1) untrusted relay attack model; 2) trusted relay with eavesdropper attack model. Finally, we conduct three simulations of our proposed scheme. The simulation results agree with the theoretical analysis illustrating that our proposed scheme can achieve a better performance than the existing schemes.
Secure information exchange occurs in many recently emerging cooperative-based networks, such as 5G networks (especially those with a Device to Device architecture), the Internet of Things, and vehicular ad hoc networks. However, the existing information exchange protocols only focus on either pairwise information exchange or group information exchange, and none of these protocols enable private and public information exchange to occur simultaneously. Thus, a general secure information exchange protocol for a multiuser channel is desirable. With this motivation, this paper investigates simultaneous private and public information exchange in a Multiple Inputs Multiple Outputs (MIMO) multiuser relay channel. In an aim to achieve this goal, signal alignment is chosen as the core technique. With the designed precoding matrix for each user, private information is aligned with its exchange partner, and public information forms a coding chain at the relay. With the aligned private signal and public coding chain, neither an untrusted relay nor external eavesdroppers can recover the original individual information. Performance analyses of the proposed protocol are conducted. First, we conduct transmission performance analyses from the perspective of time slot cost. Second, we conduct a security analysis for private information exchange and public information exchange. Third, we conduct secrecy sum-rate analysis for three attack scenarios: an untrusted relay attack only, an eavesdropper attack only, and both an untrusted relay and eavesdropper attack. The simulations are conducted to demonstrate that the proposed protocol can enable simultaneous private and public information exchange while resisting attacks by an undesired receiver, an untrusted relay, and external eavesdroppers.
Security issue has been considered as one of the most pivotal aspects for the fifth-generation mobile network (5G) due to the increasing demands of security service as well as the growing occurrence of security threat. In this paper, instead of focusing on the security architecture in the upper layer, we investigate the secure transmission for a basic channel model in a heterogeneous network, that is, two-way relay channels. By exploiting the properties of the transmission medium in the physical layer, we propose a novel secure scheme for the aforementioned channel mode. With precoding design, the proposed scheme is able to achieve a high transmission efficiency as well as security. Two different approaches have been introduced: information theoretical approach and physical layer encryption approach. We show that our scheme is secure under three different adversarial models: ( 1 ) untrusted relay attack model, ( 2 ) trusted relay with eavesdropper attack model, and ( 3 ) untrusted relay with eavesdroppers attack model. We also derive the secrecy capacity of the two different approaches under the three attacks. Finally, we conduct three simulations of our proposed scheme. The simulation results agree with the theoretical analysis illustrating that our proposed scheme could achieve a better performance than the existing schemes.
This work investigates the vulnerability of analog network coding (ANC) to physical layer attacks from adversarial users, when all nodes are equipped with multiple antennas. Specifically, we examine the MIMO two way relay channel (TWRC) with two users trying to communicate with each other via a relay node in the presence of a passive eavesdropper. We propose a new performance metric, namely the secrecy sum rate of the MIMO TWRC, to quantify performance. We then consider secure transmission strategies for the scenarios of no eavesdropper channel state information at the transmitters (ECSIT) and complete ECSIT, respectively. Finally, numerical results are presented to illustrate the improvement in secrecy obtained with the proposed transmission schemes.
Achieving secure transmission in wireless network is a significantly important research topic. Classic cryptography encrypts a confidential message to an unreadable cipher message. Thus only the authentic receiver with correct secrecy key is able to decrypt the message. However, with the growing computational capability of adversaries, the requirement of secrecy key generation and distribution is getting stringent. Another method to achieve wireless security, which has attracted much attention in recent years, is through physical layer processing, named physical layer security. In a typical wiretap channel model consisting of a transmitter, a legal receiver and an adversary (illegal receiver), early works have proven that it is possible to achieve positive secrecy rate using multiple antenna techniques, such as beamforming, at the transmitter. In this thesis, we focus on two types of malicious behaviors of the adversary: passive eavesdropping and active attack. For the passive eavesdropping, we first consider the multi-input-single-output (MISO) wiretap channel, in which the legitimate transmitter utilizes the artificial noise aided precoding strategy to maximize the achievable secrecy rate of the channel. Both scenarios of known and unknown channel state information (CSI) for the eavesdropper channels are considered. By deriving the closed-form expression of ergodic secrecy rate, we prove that there exists an optimal power ratio between the information signal and the artificial noise. We then extend our study to a four-node fading channel model in a wireless relay network, which includes two single-antenna users, one single-antenna eavesdropper and one relay node equipped with multiple antennas. By studying the decode-and-forward (DF) scheme, cooperative jamming (CJ) scheme and one proposed hybrid relay scheme, relay-and-jamming (RJ), we aims to find the optimal relay scheme with the condition that the transmitter and the relay node are under individual power constraints and the CSI of the illegitimate channel is only statistically known. Our analysis shows that the hybrid RJ scheme is optimal when the transmitter has a relatively small power budget and/or the transmitter is far away from the intended receiver. Besides the passive eavesdropping, the adversary could also choose the active attack. The pilot spoofing attack is one active attack conducted by the adversary during the channel estimation phase of the legitimate transmission. In practical systems, the pilot signals are usually known \textit{a priori} and repeatedly used information. In this attack, an intelligent adversary spoofs the transmitter on the estimation of CSI by sending the identical pilot signal as the legitimate receiver. By doing so, the adversary could obtain a larger channel rate in the data transmission phase, and also drastically weaken the strength of the received signal at the legitimate receiver if the adversary utilizes large enough power. Due to the serious consequences caused by such an attack, we first propose an energy ratio detector (ERD) that explores the asymmetry of received signal power levels at the transmitter and the legitimate receiver when the attack occurs. Our analysis shows that the ERD could provide very high probability of detection with certain requirement on the false alarming probability. Furthermore, we design a two-way training based scheme to provide not only attack detection but also secure transmission. The two-way training based detector (TWTD) exploits the intrusive component created by the adversary, followed by a secure beamforming-assisted data transmission. In addition to the good detection performance, our scheme could estimate both legitimate and illegitimate channels, with which the beamforming could be designed for data transmission.
In this letter, we propose a secure beamforming scheme for physical layer network coding (PNC)-based multiple-input multiple-output (MIMO) two-way relaying system. The relay node performs PNC mapping. An eavesdropper is attempting to intercept the user information. The channel state information (CSI) of the user-to-eavesdropper channel is imperfect at the user nodes. A robust optimization problem is formulated to design beamforming vectors at the user nodes and relay. The problem is non-convex, and an algorithm is proposed to solve that. In the numerical analysis, we discuss the convergence of the proposed algorithm and the impact of the CSI error on the performance.