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Secure Transmission with Multiple Antennas: The MISOME Wiretap Channel  [PDF]
Ashish Khisti,Gregory Wornell
Mathematics , 2007,
Abstract: The role of multiple antennas for secure communication is investigated within the framework of Wyner's wiretap channel. We characterize the secrecy capacity in terms of generalized eigenvalues when the sender and eavesdropper have multiple antennas, the intended receiver has a single antenna, and the channel matrices are fixed and known to all the terminals, and show that a beamforming strategy is capacity-achieving. In addition, we show that in the high signal-to-noise (SNR) ratio regime the penalty for not knowing eavesdropper's channel is small--a simple ``secure space-time code'' that can be thought of as masked beamforming and radiates power isotropically attains near-optimal performance. In the limit of large number of antennas, we obtain a realization-independent characterization of the secrecy capacity as a function of the number $\beta$: the number of eavesdropper antennas per sender antenna. We show that the eavesdropper is comparatively ineffective when $\beta<1$, but that for $\beta\ge2$ the eavesdropper can drive the secrecy capacity to zero, thereby blocking secure communication to the intended receiver. Extensions to ergodic fading channels are also provided.
On Secure Transmission over Parallel Relay Eavesdropper Channel  [PDF]
Zohaib Hassan Awan,Abdellatif Zaidi,Luc Vandendorpe
Mathematics , 2010,
Abstract: We study a four terminal parallel relay-eavesdropper channel which consists of multiple independent relay-eavesdropper channels as subchannels. For the discrete memoryless case, we establish inner and outer bounds on the rate-equivocation region. For each subchannel, secure transmission is obtained through one of the two coding schemes at the relay: decoding-and-forwarding the source message or confusing the eavesdropper through noise injection. The inner bound allows relay mode selection. For the Gaussian model we establish lower and upper bounds on the perfect secrecy rate. We show that the bounds meet in some special cases, including when the relay does not hear the source. We illustrate the analytical results through some numerical examples.
An Approach to Compress & Secure Image Transmission over a Noisy Channel
Ramveer Singh
Journal of Global Research in Computer Science , 2010,
Abstract: In our day to day life, requires more secure transmission whereas the transmission channel is too noisy. Transmission image in various field i.e. medical field (Telemedicine) with complete efficiency for saving human life, secrecy of communication between secret agents and their relative government, to maintain the confidentiality in military operations, etc. In our approach, we introduced a new scheme to transmit an image over noisy transmission channel. Our approach is suitable combination of cryptography and compression with removal of transmission error. Cryptography provides secure transmission, Compression increases the capacity of transmission channel and Fuzzy is used for error which gets during transmission of image. Key Words: Image, Compression, Encryption, Decryption, Secure Communication, Error Detection & Correction.
Transmission over Cognitive Radio Channel with Novel Secure LT Code  [PDF]
Elham Hosseini, Abolfazl Falahati
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.53023
Abstract:

With the increasing of communication applications in recent years, the demand for radio spectral resources has increased significantly. Cognitive radio scenario was proposed to improve spectrum efficiency in wireless communication systems. In cognitive radio network, it is essential that control information is sent securely and reliably. Ensuring the trustworthiness of the transmitting of spectrum sensing information is important in the CR networks since spectrum sensing directly affects spectrum management and incumbent coexistence. In this paper, the first secondary link channel model is presented, then a secure LT Code is proposed to be compatible with presented channel model and acquires good QoS. As we may know, LT code overcomes packet loss when the channel of the SU is reclaimed by PU. In the new proposed combined encoding and ciphered block, a LT code matrix is used to generate a symmetric cryptographic key. Thus, less complexity observed in the processing computation. Besides, cryptographic key is not sent over the channel. As a result, an attacker has no way to eavesdrop the key unless he is prepared to consider all possible key combinations. This replaced block supplies secure controlling channel and increases spectrum efficiency too.

Secure Transmission with Multiple Antennas II: The MIMOME Wiretap Channel  [PDF]
Ashish Khisti,Gregory Wornell
Mathematics , 2010,
Abstract: The capacity of the Gaussian wiretap channel model is analyzed when there are multiple antennas at the sender, intended receiver and eavesdropper. The associated channel matrices are fixed and known to all the terminals. A computable characterization of the secrecy capacity is established as the saddle point solution to a minimax problem. The converse is based on a Sato-type argument used in other broadcast settings, and the coding theorem is based on Gaussian wiretap codebooks. At high signal-to-noise ratio (SNR), the secrecy capacity is shown to be attained by simultaneously diagonalizing the channel matrices via the generalized singular value decomposition, and independently coding across the resulting parallel channels. The associated capacity is expressed in terms of the corresponding generalized singular values. It is shown that a semi-blind "masked" multi-input multi-output (MIMO) transmission strategy that sends information along directions in which there is gain to the intended receiver, and synthetic noise along directions in which there is not, can be arbitrarily far from capacity in this regime. Necessary and sufficient conditions for the secrecy capacity to be zero are provided, which simplify in the limit of many antennas when the entries of the channel matrices are independent and identically distributed. The resulting scaling laws establish that to prevent secure communication, the eavesdropper needs 3 times as many antennas as the sender and intended receiver have jointly, and that the optimimum division of antennas between sender and intended receiver is in the ratio of 2:1.
k-Connectivity in Secure Wireless Sensor Networks with Physical Link Constraints - The On/Off Channel Model  [PDF]
Jun Zhao,Osman Ya?an,Virgil Gligor
Mathematics , 2012,
Abstract: Random key predistribution scheme of Eschenauer and Gligor (EG) is a typical solution for ensuring secure communications in a wireless sensor network (WSN). Connectivity of the WSNs under this scheme has received much interest over the last decade, and most of the existing work is based on the assumption of unconstrained sensor-to-sensor communications. In this paper, we study the k-connectivity of WSNs under the EG scheme with physical link constraints; k-connectivity is defined as the property that the network remains connected despite the failure of any (k - 1) sensors. We use a simple communication model, where unreliable wireless links are modeled as independent on/off channels, and derive zero-one laws for the properties that i) the WSN is k-connected, and ii) each sensor is connected to at least k other sensors. These zero-one laws improve the previous results by Rybarczyk on the k-connectivity under a fully connected communication model. Moreover, under the on/off channel model, we provide a stronger form of the zero-one law for the 1-connectivity as compared to that given by Ya\u{g}an. We also discuss the applicability of our results in a different network application, namely in a large-scale, distributed publish-subscribe service for online social networks.
Resource Allocation in a Cognitive Radio System with Imperfect Channel State Estimation
Tao Qin,Cyril Leung,Chunyan Miao,Zhiqi Shen
Journal of Electrical and Computer Engineering , 2010, DOI: 10.1155/2010/419430
Abstract: Cognitive radio (CR) is a promising concept for improving the utilization of scarce radio spectrum resources. Orthogonal frequency division multiplexing (OFDM) is regarded as a technology which is well matched for CR systems. It is shown that channel estimation errors can result in a severe performance degradation in a multiuser OFDM CR system. A simple back-off scheme is proposed, and simulation results are provided which show that the proposed scheme is very effective in mitigating the negative impact of channel estimation errors.
Secure Transmission on the Two-hop Relay Channel with Scaled Compute-and-Forward  [PDF]
Zhijie Ren,Jasper Goseling,Jos H. Weber,Michael Gastpar
Mathematics , 2015,
Abstract: In this paper, we consider communication on a two-hop channel, in which a source wants to send information reliably and securely to the destination via a relay. We consider both the untrusted relay case and the external eavesdropper case. In the untrusted relay case, the relay behaves as an eavesdropper and there is a cooperative node which sends a jamming signal to confuse the relay when the it is receiving from the source. We propose two secure transmission schemes using the scaled compute-and-forward technique. One of the schemes is based on a random binning code and the other one is based on a lattice chain code. It is proved that in either the high Signal-to-Noise-Ratio (SNR) scenario and/or the restricted relay power scenario, if the destination is used as the jammer, both schemes outperform all existing schemes and achieve the upper bound. In particular, if the SNR is large and the source, the relay, and the cooperative jammer have identical power and channels, both schemes achieve the upper bound for secrecy rate, which is merely $1/2$ bit per channel use lower than the channel capacity without secrecy constraints. We also prove that one of our schemes achieves a positive secrecy rate in the external eavesdropper case in which the relay is trusted and there exists an external eavesdropper.
Efficient and Secure Key Extraction using CSI without Chasing down Errors  [PDF]
Jizhong Zhao,Wei Xi,Jinsong Han,Shaojie Tang,Xiangyang Li,Yunhao Liu,Yihong Gong,Zehua Zhou
Computer Science , 2012,
Abstract: Generating keys and keeping them secret is critical in secure communications. Due to the "open-air" nature, key distribution is more susceptible to attacks in wireless communications. An ingenious solution is to generate common secret keys by two communicating parties separately without the need of key exchange or distribution, and regenerate them on needs. Recently, it is promising to extract keys by measuring the random variation in wireless channels, e.g., RSS. In this paper, we propose an efficient Secret Key Extraction protocol without Chasing down Errors, SKECE. It establishes common cryptographic keys for two communicating parties in wireless networks via the realtime measurement of Channel State Information (CSI). It outperforms RSS-based approaches for key generation in terms of multiple subcarriers measurement, perfect symmetry in channel, rapid decorrelation with distance, and high sensitivity towards environments. In the SKECE design, we also propose effective mechanisms such as the adaptive key stream generation, leakage resilient consistence validation, and weighted key recombination, to fully exploit the excellent properties of CSI. We implement SKECE on off-the-shelf 802.11n devices and evaluate its performance via extensive experiments. The results demonstrate that SKECE achieves a more than 3x throughput gain in the key generation from one subcarrier in static scenarios, and due to its high efficiency, a 50% reduction on the communication overhead compared to the state-of-the-art RSS based approaches.
An Integrated Source and Channel Rate Allocation Scheme for Robust Video Coding and Transmission over Wireless Channels  [cached]
K. J. Ray Liu,Jie Song
EURASIP Journal on Advances in Signal Processing , 2004, DOI: 10.1155/s168761720430908x
Abstract: A new integrated framework for source and channel rate allocation is presented for video coding and transmission over wireless channels without feedback channels available. For a fixed total channel bit rate and a finite number of channel coding rates, the proposed scheme can obtain the near-optimal source and channel coding pair, and corresponding robust video coding scheme such that the expected end-to-end distortion of video signals can be minimized. With the assumption that the encoder has the stochastic information such as average SNR and Doppler frequency of the wireless channel, the proposed scheme takes into account robust video coding, channel coding, packetization, and error concealment techniques altogether. An improved method is proposed to recursively estimate the end-to-end distortion of video coding for transmission over error-prone channels. The proposed estimation is about 1-3 dB more accurate compared to the existing integer-pel based method. Rate-distortion optimized video coding is employed for the trade-off between coding efficiency and robustness to transmission errors.
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