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Secure Degrees of Freedom of the Gaussian Wiretap Channel with Helpers and No Eavesdropper CSI: Blind Cooperative Jamming  [PDF]
Jianwei Xie,Sennur Ulukus
Computer Science , 2013,
Abstract: We consider the Gaussian wiretap channel with M helpers, where no eavesdropper channel state information (CSI) is available at the legitimate entities. The exact secure d.o.f. of the Gaussian wiretap channel with M helpers with perfect CSI at the transmitters was found in [1], [2] to be M/(M+1). One of the key ingredients of the optimal achievable scheme in [1], [2] is to align cooperative jamming signals with the information symbols at the eavesdropper to limit the information leakage rate. This required perfect eavesdropper CSI at the transmitters. Motivated by the recent result in [3], we propose a new achievable scheme in which cooperative jamming signals span the entire space of the eavesdropper, but are not exactly aligned with the information symbols. We show that this scheme achieves the same secure d.o.f. of M/(M+1) in [1], [2] but does not require any eavesdropper CSI; the transmitters blindly cooperative jam the eavesdropper.
Secure Wireless Information and Power Transfer in Large-Scale MIMO Relaying Systems with Imperfect CSI  [PDF]
Xiaoming Chen,Jian Chen,Tao Liu
Mathematics , 2014,
Abstract: In this paper, we address the problem of secure wireless information and power transfer in a large-scale multiple-input multiple-output (LS-MIMO) amplify-and-forward (AF) relaying system. The advantage of LS-MIMO relay is exploited to enhance wireless security, transmission rate and energy efficiency. In particular, the challenging issues incurred by short interception distance and long transfer distance are well addressed simultaneously. Under very practical assumptions, i.e., no eavesdropper's channel state information (CSI) and imperfect legitimate channel CSI, this paper investigates the impact of imperfect CSI, and obtains an explicit expression of the secrecy outage capacity in terms of transmit power and channel condition. Then, we propose an optimal power splitting scheme at the relay to maximize the secrecy outage capacity. Finally, our theoretical claims are validated by simulation results.
On the Performance of Selection Cooperation with Outdated CSI and Channel Estimation Errors  [PDF]
Mehdi Seyfi,Sami Muhaidat,Jie Liang
Mathematics , 2011,
Abstract: In this paper, we investigate the performance of selection cooperation in the presence of imperfect channel estimation. In particular, we consider a cooperative scenario with multiple relays and amplify-and-forward protocol over frequency flat fading channels. In the selection scheme, only the "best" relay which maximizes the effective signal-to-noise ratio (SNR) at the receiver end is selected. We present lower and upper bounds on the effective SNR and derive closed-form expressions for the average symbol error rate (ASER), outage probability and average capacity per bandwidth of the received signal in the presence of channel estimation errors. A simulation study is presented to corroborate the analytical results and to demonstrate the performance of relay selection with imperfect channel estimation.
Secure On-Off Transmission Design with Channel Estimation Errors  [PDF]
Biao He,Xiangyun Zhou
Mathematics , 2013,
Abstract: Physical layer security has recently been regarded as an emerging technique to complement and improve the communication security in future wireless networks. The current research and development in physical layer security is often based on the ideal assumption of perfect channel knowledge or the capability of variable-rate transmissions. In this work, we study the secure transmission design in more practical scenarios by considering channel estimation errors at the receiver and investigating both fixed-rate and variable-rate transmissions. Assuming quasi-static fading channels, we design secure on-off transmission schemes to maximize the throughput subject to a constraint on secrecy outage probability. For systems with given and fixed encoding rates, we show how the optimal on-off transmission thresholds and the achievable throughput vary with the amount of knowledge on the eavesdropper's channel. In particular, our design covers the interesting case where the eavesdropper also uses the pilots sent from the transmitter to obtain imperfect channel estimation. An interesting observation is that using too much pilot power can harm the throughput of secure transmission if both the legitimate receiver and the eavesdropper have channel estimation errors, while the secure transmission always benefits from increasing pilot power when only the legitimate receiver has channel estimation errors but not the eavesdropper. When the encoding rates are controllable parameters to design, we further derive both a non-adaptive and an adaptive rate transmission schemes by jointly optimizing the encoding rates and the on-off transmission thresholds to maximize the throughput of secure transmissions.
Enhanced Transmit Antenna Selection Scheme for Secure Throughput Maximization Without CSI at the Transmitter and its Applications on Smart Grids  [PDF]
Hirley Alves,Mauricio Tomé,Pedro H. J. Nardelli,Carlos H. M. de Lima,Matti Latva-aho
Mathematics , 2015,
Abstract: This paper addresses the establishment of secure communication links between smart-meters (Alice) and an aggregator (Bob) in the presence of an eavesdropper (Eve). The proposed scenario assumes: (i) MIMOME wiretap channel; (ii) transmit antenna selection at the Alice; (iii) no channel state information at the transmitter; (iv) fixed Wyner codes; and (v) guarantee of secure throughput by both quality of service and secrecy outage constraints. We propose a simple protocol to enhance security via transmit antenna selection, and then assess its performance in closed-form by means of secrecy outage and successful transmission probabilities. We assume these probabilities are our constraints and then maximize the secure throughput, establishing a security-reliability trade-off for the proposed scenario. Our numerical results illustrate the effect of this trade-off on the secure throughput as well as on the number of antennas at Alice, Bob and Eve. Interestingly, a small sacrifice in reliability allows secrecy enhancement in terms of secure bps/Hz. We apply this idea in our smart grid application to exemplify that, although Eve may acquire some samples of the average power demand of a household, it is not enough to properly reconstruct such curve.
Secure Satellite Communication Systems Design with Individual Secrecy Rate Constraints  [PDF]
Jiang Lei,Zhu Han,M. A. Vázquez-Castro,Are Hj?rungnes
Mathematics , 2011, DOI: 10.1109/TIFS.2011.2148716
Abstract: In this paper, we study multibeam satellite secure communication through physical (PHY) layer security techniques, i.e., joint power control and beamforming. By first assuming that the Channel State Information (CSI) is available and the beamforming weights are fixed, a novel secure satellite system design is investigated to minimize the transmit power with individual secrecy rate constraints. An iterative algorithm is proposed to obtain an optimized power allocation strategy. Moreover, sub-optimal beamforming weights are obtained by completely eliminating the co-channel interference and nulling the eavesdroppers' signal simultaneously. In order to obtain jointly optimized power allocation and beamforming strategy in some practical cases, e.g., with certain estimation errors of the CSI, we further evaluate the impact of the eavesdropper's CSI on the secure multibeam satellite system design. The convergence of the iterative algorithm is proven under justifiable assumptions. The performance is evaluated by taking into account the impact of the number of antenna elements, number of beams, individual secrecy rate requirement, and CSI. The proposed novel secure multibeam satellite system design can achieve optimized power allocation to ensure the minimum individual secrecy rate requirement. The results show that the joint beamforming scheme is more favorable than fixed beamforming scheme, especially in the cases of a larger number of satellite antenna elements and higher secrecy rate requirement. Finally, we compare the results under the current satellite air-interface in DVB-S2 and the results under Gaussian inputs.
Errors and Their Mitigation at the Kirchhoff-Law-Johnson-Noise Secure Key Exchange  [PDF]
Yessica Saez, Laszlo B. Kish
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0081103
Abstract: A method to quantify the error probability at the Kirchhoff-law-Johnson-noise (KLJN) secure key exchange is introduced. The types of errors due to statistical inaccuracies in noise voltage measurements are classified and the error probability is calculated. The most interesting finding is that the error probability decays exponentially with the duration of the time window of single bit exchange. The results indicate that it is feasible to have so small error probabilities of the exchanged bits that error correction algorithms are not required. The results are demonstrated with practical considerations.
Chasing beams and muon colliders  [PDF]
G. Mambriani,R. Coisson
Physics , 2014,
Abstract: A possible alternative way of producing muons (or other unstable particles) for colliders is proposed. It consists in colliding beams in a "chasing beam" configuration, i.e. collisions of two beams having the same direction but with different energies. This would produce muons with a good collimation, having already a high energy from the beginning, and then a longer life.
Quantification of group chasing and escaping process  [PDF]
S. Matsumoto,A. Kamimura,T. Nogawa,T. Shimada,N. Ito,T. Ohira
Physics , 2012,
Abstract: We study a simple group chase and escape model by introducing new parameters with which configurations of chasing and escaping in groups are classified into three characteristic patterns. In particular, the parameters distinguish two essential configurations: a one-directional formation of chasers and escapees, and an escapee surrounded by chasers. In addition, pincer movements and aggregating processes of chasers and escapees are also quantified. Appearance of these configurations highlights efficiency of hunting during chasing and escaping.
Chasing diagrams in cryptography  [PDF]
Dusko Pavlovic
Mathematics , 2014,
Abstract: Cryptography is a theory of secret functions. Category theory is a general theory of functions. Cryptography has reached a stage where its structures often take several pages to define, and its formulas sometimes run from page to page. Category theory has some complicated definitions as well, but one of its specialties is taming the flood of structure. Cryptography seems to be in need of high level methods, whereas category theory always needs concrete applications. So why is there no categorical cryptography? One reason may be that the foundations of modern cryptography are built from probabilistic polynomial-time Turing machines, and category theory does not have a good handle on such things. On the other hand, such foundational problems might be the very reason why cryptographic constructions often resemble low level machine programming. I present some preliminary explorations towards categorical cryptography. It turns out that some of the main security concepts are easily characterized through the categorical technique of *diagram chasing*, which was first used Lambek's seminal `Lecture Notes on Rings and Modules'.
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