Browsing by Author "El Shafie, Ahmed"
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Item Impact of Passive and Active Security Attacks on MIMO Smart Grid Communications(Institute of Electrical and Electronics Engineers Inc.) El Shafie, Ahmed; Chihaoui, H.; Hamila, R.; Al-Dhahir, Naofal; Gastli, A.; Ben-Brahim, L.; 0000-0002-7315-8242 (El Shafie, A); El Shafie, Ahmed; Al-Dhahir, NaofalWe consider multiple source nodes (consumers) communicating wirelessly their energy demands to the meter data-management system (MDMS) over the subarea gateway(s). We quantify the impact of passive and active security attacks on the reliability and security of the wireless communications system and the energy-demand estimation error cost in dollars incurred by the utility. We adopt a multiple-input multiple-output (MIMO) multiantenna-eavesdropper wiretap channel model. To secure the MIMO wireless communication system, the legitimate nodes generate artificial noise signals to mitigate the effect of the passive eavesdropping security attacks. Furthermore, we propose a redundant gateway design where multiple gateways are assumed to coexist in each subarea to forward the consumers’ energy-demand messages. We quantify the redundant designs impact on the communication reliability between the consumers and the MDMS and on the energy-demand estimation error cost.Item PHY Security of Wiretap Channels: From Point-to-Point to Multiple Access(2018-05) El Shafie, Ahmed; 0000-0002-7315-8242 (El Shafie, A); Al-Dhahir, NaofalInformation secrecy is crucial to a wireless communication system due to the broadcast nature of radio-frequency transmissions. Traditionally, secrecy has been provided by designing upper-layer sophisticated protocols. More specifically, the problem of securing the information from malicious eavesdropping nodes has been tackled by relying on the conventional encryption mechanism. To improve the system security, physical-layer (PHY) security has been recently recognized as a valuable tool to guarantee information-theoretic confidentiality of messages transmitted over the wireless medium. In this dissertation, we propose new efficient schemes to secure the wireless links of various wireless communications networks. We investigate both the frequency non-selective and selective channels for different relaying networks. For the frequency-selective channels, we use the orthogonal-frequency division-multiplexing (OFDM) transmission scheme to convert the channel into a set of flat-faded sub-channels where each OFDM block begins with a cyclic-prefix sequence to eliminate the inter-block interference. For frequency-selective and non-selective channels, we propose secure schemes and evaluate their performance. Our proposed artificial noise aided schemes are based on the spatial and temporal degrees of freedom provided by the multiple antennas at the legitimate nodes and the cyclic prefix of the OFDM systems, respectively. We provide in-depth analysis for the PHY security of many wireless systems architectures including single-input single-output (SISO) systems, relay-aided SISO systems, multiple-input multiple-output (MIMO) systems, and relay-aided MIMO systems. In addition, we investigate the impact of data buffers at communicating nodes as well as the presence of friendly jamming nodes on the achievable secrecy rates. The duplexity capabilities of the relay nodes are also investigated and their impacts on the achievable secrecy rates are quantified. To make the communication systems more robust against eavesdropping, we also investigate securing wireless networks in the presence of a set of untrusted relay nodes where the relay nodes are assumed to be honest but curious as in, e.g., the aggregating units in the smart grids, and the servers in governmental intelligence systems. As a case study on the impact of passive and active security attacks, we quantified the gain of our proposed encoding and secure schemes in terms of improving the demand-side management's security and reducing the monetary loss to the utility.Item Secure Sum-Rate Optimal MIMO Multicasting over Medium-Voltage NB-PLC Networks(Institute of Electrical and Electronics Engineers Inc.) Elsamadouny, Ahmed; El Shafie, Ahmed; Abdallah, M.; Al-Dhahir, Naofal; 0000-0002-2716-7658 (Elsamadouny, A); 113149196515374792028 (Al-Dhahir, N); Elsamadouny, Ahmed; El Shafie, Ahmed; Al-Dhahir, NaofalWe propose a multiple-input multiple-output orthogonal frequency-division multiplexing transceiver for narrowband power-line communication applications in multi-user medium-voltage multicasting networks. The 3-phase medium-voltage multicasting network is modeled as a 2-input/3-output multiple-input multiple-output frequency-selective channel over the 3-500 kHz frequency band. We design the optimal spatial precoder, spatial power allocation, and frequency bit loading profile which maximize the sum-rate of the multicasting groups. In addition, we propose two schemes to secure data transmission through the two-group multicasting network. The first scheme secures the network when the eavesdropper is a user in one of the two multicasting groups and, hence, its channel state information is known at the transmitter. The second scheme secures the multicasting network from external passive eavesdroppers and, hence, the channels between the transmitter and the eavesdroppers are assumed to be unknown at the transmitter. The secrecy rate is evaluated for both scenarios. ©2016 IEEE.Item Security-Enhanced SC-FDMA Transmissions Using Temporal Artificial-Noise and Secret Key Aided Schemes(IEEE-Inst Electrical Electronics Engineers Inc, 2019-01-19) Marzban, Mohamed F.; El Shafie, Ahmed; Al-Dhahir, Naofal; Hamila, Ridha; 0000-0002-7214-0745 (Marzban, MF); 0000-0002-7315-8242 (EL Shafie, A); 113149196515374792028 (Al-Dhahir, N); Marzban, Mohamed F.; El Shafie, Ahmed; Al-Dhahir, NaofalWe investigate the physical-layer security of uplink single-carrier frequency-division multiple-access (SC-FDMA) systems. Multiple users, Alices, send confidential messages to a common legitimate base-station, Bob, in the presence of an eavesdropper, Eve. To secure the legitimate transmissions, each user superimposes an artificial noise (AN) signal on the time-domain SC-FDMA data symbol. We reduce the computational and storage requirements at Bob's receiver by assuming simple per-sub-channel detectors. We assume that Eve has global channel knowledge of all links in addition to high computational capabilities, where she adopts high-complexity detectors such as single-user maximum likelihood (ML), multi-user minimum-mean-square-error, and multi-user ML. We analyze the correlation properties of the time-domain AN signal and illustrate how Eve can exploit them to reduce the AN effects. We prove that the number of useful AN streams that can degrade Eve's signal-to-noise ratio is dependent on the channel memories of Alices-Bob and Alices-Eve links. Furthermore, we enhance the system security for the case of partial Alices-Bob channel knowledge at Eve, where Eve only knows the precoding matrices of the data and AN signals instead of knowing the entire Alices-Bob channel matrices, and propose a hybrid security scheme that integrates temporal AN with channel-based secret key extraction.Item Wiretap TDMA Networks with Energy-Harvesting Rechargeable-Battery Buffered Sources(Institute of Electrical and Electronics Engineers Inc, 2019-01-25) El Shafie, Ahmed; Al-Dhahir, Naofal; Ding, Zhiguo; Duong, Trung Q.; Hamila, Ridha; 113149196515374792028 (Al-Dhahir, N); Al-Dhahir, NaofalWe investigate the physical-layer security of an uplink wireless time-division multiple-access channel with energy-harvesting source nodes. We consider a set of source nodes equipped with rechargeable batteries and information buffers communicating confidentially with a base station, Bob, in the presence of a passive eavesdropper, Eve. An energy-harvesting rechargeable-battery cooperative jammer is assumed to assist the source nodes to confidentially send their information messages. We propose a two-level optimization formulation to improve the system's security performance. At the first optimization level, we propose a jamming scheme under energy constraints at different nodes to reduce the secrecy outage probabilities without relying on the eavesdropper's instantaneous channel state information. At the second optimization level, we optimize the number of energy packets used at the source nodes and the cooperative jammer as well as the time-slot allocation probabilities to maximize the secure throughput under the network's queues stability constraints and an application-specific secure throughput for each legitimate source node. The numerical results show the significant performance gains of our proposed optimization relative to two important benchmarks. We verify our theoretical findings through simulations and quantify the impact of key system design parameters on the security performance.