This paper proposes a secure transmission scheme based on the twice channel estimation in a three- node MIMO system according to the malicious pilot contamination. Firstly, the pilot transmission length is divided into two segments during the reverse training stage and the legitimate receiver allocates all the power to one arbitrary segment for transmitting the pilot. Then, the transmitter obtains the approximate estimation of the eavesdropping channel and an erroneous CSI of the main channel based on the twice channel estimation. After eliminating the eavesdropping channel from the erroneous CSI, the transmitter transmits both the signal and the artificial noise based on the modified CSI to ensure the transmission. Finally, the simulation results show that the proposed scheme significantly improves the security performance.
This paper proposes a secure transmission scheme based on the twice channel estimation in a three- node MIMO system according to the malicious pilot contamination. Firstly, the pilot transmission length is divided into two segments during the reverse training stage and the legitimate receiver allocates all the power to one arbitrary segment for transmitting the pilot. Then, the transmitter obtains the approximate estimation of the eavesdropping channel and an erroneous CSI of the main channel based on the twice channel estimation. After eliminating the eavesdropping channel from the erroneous CSI, the transmitter transmits both the signal and the artificial noise based on the modified CSI to ensure the transmission. Finally, the simulation results show that the proposed scheme significantly improves the security performance.
This paper considers a MIMO communication system that includes a transmitter, a legitimate receiver and an eavesdropper. In such a scenario, the eavesdropper has the knowledge of the pilot and utilizes pilot contamination to reduce the secrecy rate. Firstly, we analyze the effects of malicious pilot contamination on channel estimation. The more the pilot contamination power is, the more the eavesdropping performance enhances, by deducing the secrecy rate and its asymptotic expression in the data transmission phase. Besides, the optimal power allocation scheme for a full-duplex eavesdropper to simultaneously transmit pilot contamination and noise jamming is further studied. Simulation results show that the average secrecy rate with pilot contamination is 0.899bits/s/Hz less than that with noise jamming when the jamming power is 10 mW.
The pilot contamination attack is one kind of active eavesdropping activities conducted by a malicious user during the channel training phase. In the existing physical layer transmission against such attack, it is usually assumed that the transmitters may obtain prior knowledge to identify the legitimate users first, then design secure scheme based on the corrected main channel information. However, sometimes it is likely that the prior knowledge is not available, which makes it more difficult to design the transmitting scheme. Motivated by this, we propose a novel transmission against the pilot contamination attack. In our scheme, it is assumed that ideal prior knowledge of the main channel state information (CSI) is not available. Additionally, an extra assistant node is introduced to the well-known Wyner eavesdropping model. Both the uncorrected main CSI and the CSI at the assistant node are used to design the random scrambling scheme at the transmitter, which means there is no need to differentiate between eavesdroppers and legitimate users. Furthermore, we discuss the receiving performance of legitimate users cooperated with the assistant node. Numerical results shows that the legitimate users could achieve pleasant receiving performance while eavesdroppers could hardly obtain acceptable recovery of the original signal.
In a multi-antenna time-division duplex (TDD) communication system, due to channel reciprocity, the downlink channel state information can be obtained by conducting uplink training. In a wire-tap channel, an active eavesdropper can perform active eavesdropping by pilot spoofing attack. In such an attack, the eavesdropper, during the uplink training phase, transmits the identical pilot sequence as that of the legitimate receiver to the transmitter. As a result, the estimated channel by the transmitter is a weighted sum of the legitimate channel and the eavesdropping channel. Motivated by the seriousness of pilot spoofing attack, in this paper, we propose a two-stage uplink training method for pilot spoofing attack detection and secure transmission. Using the new training method, the legitimate channel and the eavesdropping channel can be correctly estimated separately. Then we propose a pilot spoofing attack detector followed by a beamforming scheme for secure data transmission. Simulation results have shown that our proposed method achieves higher detection probability, and larger secrecy rate than previously proposed anti-pilot spoofing methods.
Existing studies on physical layer security often assume the availability of perfect channel state information (CSI) and overlook the importance of channel training needed for obtaining the CSI. In this letter, we discuss how an active eavesdropper can attack the training phase in wireless communication to improve its eavesdropping performance. We derive a new security attack from the pilot contamination phenomenon, which targets at systems using reverse training to obtain the CSI at the transmitter for precoder design. This attack changes the precoder used by the legitimate transmitter in a controlled manner to strengthen the signal reception at the eavesdropper during data transmission. Furthermore, we discuss an efficient use of the transmission energy of an advanced full-duplex eavesdropper to simultaneously achieve a satisfactory eavesdropping performance whilst degrading the detection performance of the legitimate receiver.
In a time-division duplex (TDD) based multi-input single-output (MISO) system, the channel state information (CSI) can be obtained during the channel estimation phase in which the receiver transmits the pilot symbols to the transmitter. This scheme may suffer from a so-called pilot spoofing attack, i.e., an adversary may send identical pilot signals as those of the legitimate receiver to spoof the transmitter. The resultant channel estimate may then contain the CSI of both legitimate and illegitimate receivers, and if such estimated channel is used for transmit beamforming, the information dedicated for legitimate receiver will leak to the illegitimate receiver. In this paper, we study the detection and defending strategies for such pilot spoofing attack. A two-way training based scheme is proposed. The durations of the training periods are also designed to optimize the secrecy rate. Finally, numerical results are presented to show the performance of our proposed method.
In this paper, a secure communication model for cognitive multi-user massive multiple-input multiple-output (MIMO) systems with underlay spectrum sharing is investigated. A secondary (cognitive) multi-user massive MIMO system is operated by using underlay spectrum sharing within a primary (licensed) multi-user massive MIMO system. A passive multi-antenna eavesdropper is assumed to be eavesdropping upon either the primary or secondary confidential transmissions. To this end, a physical layer security strategy is provisioned for the primary and secondary transmissions via artificial noise (AN) generation at the primary base-station (PBS) and zero-forcing precoders. Specifically, the precoders are constructed by using the channel estimates with pilot contamination. In order to degrade the interception of confidential transmissions at the eavesdropper, the AN sequences are transmitted at the PBS by exploiting the excess degrees-of-freedom offered by its massive antenna array and by using random AN shaping matrices. The channel estimates at the PBS and secondary base-station (SBS) are obtained by using non-orthogonal pilot sequences transmitted by the primary user nodes (PUs) and secondary user nodes (SUs), respectively. Hence, these channel estimates are affected by intra-cell pilot contamination. In this context, the detrimental effects of intra-cell pilot contamination and channel estimation errors for physical layer secure communication are investigated. For this system set-up, the average and asymptotic achievable secrecy rate expressions are derived in closed-form. Specifically, these performance metrics are studied for imperfect channel state information (CSI) and for perfect CSI, and thereby, the secrecy rate degradation due to inaccurate channel knowledge and intra-cell pilot contamination is quantified. Our analysis reveals that a physical layer secure communication can be provisioned for both primary and secondary massive MIMO systems even with the channel estimation errors and pilot contamination.