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    A New Scheme for Provable Secure Anonymous Proxy Signature in the Standard Model

    , M.Sc. Thesis Sharif University of Technology Toluee, Rahim (Author) ; Salmasizadeh, Mahmoud (Supervisor)
    Abstract
    In order to protect the proxy signers’ privacy, many anonymous proxy signature schemes have been proposed. As far as we know, there is no provable secure anonymous proxy signature scheme without random oracles. Because the provable security in the random oracle model has received a lot of criticism, in this thesis, the aim is proposing the first provable secure anonymous proxy signature in the standard model based on existing standard assumptions.It is shown in the standard model that, the proposal is anonymous against full key exposure and existential unforgeable with the computational Diffie Hellman (CDH) and Subgroup Hiding (SGH) assumptions in bilinear groups.To provide anonymity for proxy... 

    An efficient lattice-based threshold signature scheme using multi-stage secret sharing

    , Article IET Information Security ; Volume 15, Issue 1 , 2021 , Pages 98-106 ; 17518709 (ISSN) Pilaram, H ; Eghlidos, T ; Toluee, R ; Sharif University of Technology
    John Wiley and Sons Inc  2021
    Abstract
    Secret sharing is a cryptographic technique used in many different applications such as cloud computing, multi-party computation and electronic voting. Security concerns in these applications are data privacy, availability, integrity and verifiability, where secret sharing provides proper solutions. The authors address some important features like verifiability and being multi-stage to make it usable in various field of application. Here, the authors propose an anonymous threshold signature scheme based on the trapdoor function introduced by Micciancio and Peikert by sharing the private key using a lattice-based threshold multi-stage secret sharing (TMSSS) scheme. Then, the authors improve... 

    A new ring signature scheme

    , Article 2013 10th International ISC Conference on Information Security and Cryptology, ISCISC 2013 ; 2013 Toluee, R ; Asaar, M. R ; Salmasizadeh, M ; Sharif University of Technology
    2013
    Abstract
    In current ring signature schemes, there is no distinguishing about the ranks of members of the ring. This paper proposes a ring signature scheme which considers the members' rank values. We show our scheme is anonymous against full key exposure attack and unforgeable with respect to insider corruption in the standard model with the computational Diffie Hellman (CDH) and Subgroup Hiding (SGH) assumptions in bilinear groups  

    Attribute-based ring signatures: Security analysis and a new construction

    , Article 2013 10th International ISC Conference on Information Security and Cryptology ; 2013 Toluee, R ; Asaar, M. R ; Salmasizadeh, M ; Sharif University of Technology
    IEEE Computer Society  2013
    Abstract
    In this study, we review attribute-based ring signature schemes. Our proposal presents two contributions; the first one is security analysis of Wenqiang et al.'s scheme in 2009 by presenting an attack in which we show that their scheme is forgeable. The second contribution is an efficient attribute-based ring signature scheme with constant size and constant number of pairing operations. Our scheme is unconditionally anonymous and unforgeable in the standard model. The security of our proposal is based on Static Diffie Hellman (SDH) problem. Compared with the existing attribute-based ring signature scheme with constant size, the length of the signature and the pairing operations in our scheme... 

    Investigation of Impurities and Structural Defects in Graphene

    , M.Sc. Thesis Sharif University of Technology Rostami, Melika (Author) ; Faez, Rahim (Supervisor)
    Abstract
    In this thesis the effects of impurities and different defects on electrical and magnetic properties of monolayer and bilayer graphene is investigated. Calculations are performed using density function theory. Alloying monolayer graphene with boron and nitrogen the energy gaps of 0.7 and 0.6 eV are obtained, respectively. Moreover, we show that BN is a good candidate for opening the band gap in graphene. Alloying monolayer graphene with BN the energy gap of 1.2 eV is obtained. Another way of opening band gap is to somehow break the symmetry between layers of the bilayer graphene. By alloying one layers of bilayer graphene with B, N or B-N, although the symmetry of layers is broken, each... 

    Simulation of Graphene Nanoribbon based Photodetector

    , M.Sc. Thesis Sharif University of Technology Faramarzi, Vahid (Author) ; Faez, Rahim (Supervisor)
    Abstract
    In this work, we have simulated graphene nanoribbon based photodetector and impact of changing the width, and Boron-Nitride doping and Stone-Wales defects on the optical properties of GNR has study. The energy band structure of GNR with nearest-neighbor approximation in a tight binding model calculated. To correspond with experiment and accuracy, we need to consider the impact of third nearest neighbors and edge bond relaxation. By Using the band structure, we calculated joint density of state and optical matrix elements and obtain inter band selection rule for A-GNR and Z-GNR. Then, using the Fermi’s golden rule, we investigate optical properties of GNR such as optical conductivity and... 

    A Simulation Study of Graphene Nanoribbon Field Effect Transistor

    , M.Sc. Thesis Sharif University of Technology Samadi, Mohsen (Author) ; Faez, Rahim (Supervisor)
    Abstract
    In this thesis, a field effect transistor (FET) using armchair graphene nanoribbon as the channel is simulated, and the effects of changing nanoribbon width and length, as well as adding defects, are also studied. To obtain the Hamiltonian matrix and the energy band structure of graphene nanoribbon, tight binding method is used in which the first and third neighbor approximation is considered. Also, to maximize accuracy, we also considered the edge bond reconstruction. To obtain the transport characteristics of the transistor, such as the transmission coefficient and the density of states (DOS), Poisson and Schrodinger equations are solved self-consistently. We used the nonequilibrium... 

    Design of Graphene Spintronic Devices

    , M.Sc. Thesis Sharif University of Technology Barami, Soode (Author) ; Faez, Rahim (Supervisor)
    Abstract
    Magnetization have an important role in spintronic devices based on graphene. In this study the effect of stone-wales and vacancy defect on electrical and magnetic properties of zigzag and armchair graphene nanoribbons were investigated. Calculations are performed using tight-binding and hubard model combining with Green's function techniques. When the balance between A and B sub-lattices gets disturbed, magnetization will be appeared. In stone-wales defect we have local magnetization because of changing the position of sub-lattices and the total magnetization is zero. In addition the stone-wales defect can change and modify the band structures and band gaps. Vacancy of carbon atom in... 

    Simulation of Organic Solar Cells

    , M.Sc. Thesis Sharif University of Technology Bahrami, Ali (Author) ; Faez، Rahim (Supervisor)
    Abstract
    Solar cells are one of the most promising clean and readily available energy sources. Organic solar cells as a new generation of solar cells, have attracted strong attention in recent years, due to the advantages of flexibility, thinness, and simple manufacturing process. This work focuses on the electrical processes in organic solar cells and approaches for enhancing the efficiency of solar cell by employing two-dimensional drift-diffusion model. At the first step. We investigate the role of different parameters such as mobility (considering different recombination mechanisms), active layer thickness, light intensity, barrier injections and energetic disorder on the performance of single... 

    Design and Simulation of Panchromatic Organic Photodetector

    , M.Sc. Thesis Sharif University of Technology Meraji, Omid (Author) ; Faez, Rahim (Supervisor)
    Abstract
    Organic photodetectrors(OPD) are new generation of photodetectors that use of organic materials to convert optical signal to electrical current. Organic photodetectors in recent decade have witnessed significant improvements and many recent research allocated to this photodetectors. This OPD’s have important application so that the inorganic photodetectors have some problems in that application , for example: wide area imagination , biomedical sensors , flexible application and . . . .This work focus on the design and simulation of a panchromatic photodetector that use of new material and have high bandwidth and low dark current. One of application of this OPD is to use in optical... 

    Simulation and Comparative Study of Tunneling FETs Based on Graphene Nanoribbon and Phosphorene Monolayer

    , M.Sc. Thesis Sharif University of Technology Almasi, Hossein (Author) ; Faez, Rahim (Supervisor)
    Abstract
    In this thesis, we simulate and investigate two transistors which both have tunneling FET (TFET) structure but the channel in the first one is graphene nanoribbon (GNR) and in the second one is a monolayer of phosphorene (PML). To describe the quantum systems of the transistors, we use the tight binding method and its models for the channel materials. In case of the PML TFET, based on the behavior of the phosphorene nanoribbon in different widths, we obtain a proper amount for the width to model the infinite-width channel. To extract the channel quantum transport, the Schrodinger-Poisson equations are self-consistently solved. In the next step, we simulate the GNR TFET and present the... 

    Modeling and Simulation of a High Power Photoconductive Semiconductor Switch (PCSS)

    , M.Sc. Thesis Sharif University of Technology Hemmat, Zahra (Author) ; Faez, Rahim (Supervisor)
    Abstract
    There are a wide variety of light-triggered switches. Photoconductive semiconductor switches (PCSSs) have been investigated intensively for many applications owing to their unique advantages over other switches. The advantages of PCSSs make them a perfect choice for many important applications where high switching accuracy and high-power capability are required. Photoconductive switches are fabricated from a variety of semiconductors, including silicon carbide (SiC), gallium arsenide (GaAs) and gallium nitride (GaN). In Photoconductive semiconductor switches (PCSSs) the switching mechanism is initiated by optical illumination and laser source controls the flow of current. In the off or... 

    Simulation and Analysis Graphene Based Bio-chemical Sensor Using Localized Surface Plasmon Resonance

    , M.Sc. Thesis Sharif University of Technology Tareh, Batool (Author) ; Faez, Rahim (Supervisor)
    Abstract
    One of the different sensing techniques for biosensors is based on surface plasmon resonance which provides high reliability and efficiency. In this project working operating principles of biosensors based on surface plasmon resonance will be examined. For investigation of sensing meachanism we assume that there an array consisting of alternating graphen ribbons which by applying light leads to an effective magnetic field coupling to the localized surface plasmon. The numerical calculations are based on the exact solution of Maxwell's equation using Fuorier Model Method and Matlab coding. In these calculations, the coefficients of transmission, reflection and absorption of light versus... 

    Ferromagnetic Single Electron Transistor

    , M.Sc. Thesis Sharif University of Technology Asgari, Somaieh (Author) ; Faez, Rahim (Supervisor)
    Abstract
    This thesis completely introduses ferromagnetic single electron transistor while that identifies the application and types of the transistor.Master equation is used for simulationing of the transistor. This simulation is divided to two general sections.In the first section proposed thermal equilibrium the normal island and The two spin subsystems , however, are in thermal equilibrium and quantized nature of energy spectrum of a small central electrode and fluctuations in the spin accumulation were ignored , however, we simplify the problem and assume that the charging energy are independent of the electron distribution, and number of electrons in the normal island. ،hat tunnel rates can be... 

    Quantum Dot Infrared Photodetector

    , M.Sc. Thesis Sharif University of Technology Davari, Narges (Author) ; Faez, Rahim (Supervisor)
    Abstract
    Conventionally all objects radiate most of its energy in the from of infrared waves, therefore, infrared photodetectors for detecting objects is important and more study is done on improve the detecting parameters. The proposed structures are developed from bulk to quantum well and quantum dots in recently years. In this work at reason insensitivity to incident light polarization, flexible operation wavelength, high operation temperature, inherent photovoltaic effect, low capture probability we study the structure of quantum dot infrared photodetectors and then for improve the detecting parameters structure of two layers quantum dot separated with a layer thin barrier (bilayer). And then a... 

    Intelligent based trajectory planning in Terrain Following flight

    , Article 25th Congress of the International Council of the Aeronautical Sciences 2006, Hamburg, 3 September 2006 through 8 September 2006 ; Volume 5 , 2006 , Pages 3169-3175 Rahim, M ; Malaek, S. M ; Sharif University of Technology
    Curran Associates Inc  2006
    Abstract
    A novel approach in Terrain Following/Terrain Avoidance (TF/TA) flight is proposed that facilitates flying over unknown terrains. Intelligency is implemented using fuzzy decision making tools. This method can be used in offline design in trajectory planning which has wide applications in TF/TA. A relationship b etween slope of terrain and aircraft height with speed of aircraft is constructed by fuzzy approach  

    Quantum Well Solar Cell

    , M.Sc. Thesis Sharif University of Technology ZareBidaki, Homa (Author) ; Faez, Rahim (Supervisor)
    Abstract
    In this thesis, the goal is to improve the efficiency of quantum and solar cell. The effect of quantum wells was simulated by Silvaco. Initially, the quantum well has been adjusted to a cell junction GaAs. Then, using quantum wells in cell junction towing and three, improving short-circuit, the returns will be 53.79% and 54.33%. This efficiency is about 10% more than the triple-junction solar cells. To improve the efficiency effects of layer thicknesses, parameters, and the number of quantum wells were studied.Tandem cell is 〖In〗_0.51 〖Ga〗_0.49 P/GaAs, and triple is 〖In〗_0.51 〖Ga〗_0.49 P/GaAs/〖In〗_0.28 〖Ga〗_0.72 As. By adjusting the quantum well and sandwiching the well layers staggered by... 

    Simulation And Analysis of Terahertz Laser Based on Graphene

    , M.Sc. Thesis Sharif University of Technology Abdolzadeh, Parvin (Author) ; Faez, Rahim (Supervisor)
    Abstract
    Graphene, a monolayer carbon-atomic honeycomb lattice crystal, has attracted attention due to its peculiar carrier transport properties owing to the gapless energy spectrum. Due to lack of applicable light source in terahertz (THz) band, further researches to finding materials that are suitable for semiconductor lasers in this band to be continued. In this thesis, the population inversion possibility that is the first provision of laser operation, was analyzed in graphene optical pumping situation. The analysis was done by numerical solving of carrier concentration and energy density relations.As a result of this analysis population inversion is obtained when the stimulation square pulse has... 

    Simulation and Analysis of Bilayer Graphene FET with Defect

    , M.Sc. Thesis Sharif University of Technology Ghalehkohneh, Ali (Author) ; Faez, Rahim (Supervisor)
    Abstract
    In this thesis, a field-effect transistor using armchair bilayer grapheme nanoribbon as channel material in simulated. In first, electronic property of bilayer graphene and bilayer graphene nanoribbons using tight binding are studied. Transport properties of transistor, sush as transsmition and density of carriers, are studied by self-consistently solving poisson equation and Non-Equilibrium Green’s Function. Finally, I-V characteristics of the transistor can be obtained using the Landauer formula.
    Also, effect of Stone-Wales defect on bandstructure and transmission of armchair bilayer grapheme nanoribbon is investigated. This defect increases energy gap and broadens egergy bands in... 

    Robust flutter analysis and control of a wing

    , Article Aircraft Engineering and Aerospace Technology ; Volume 84, Issue 6 , 2012 , Pages 423-438 ; 00022667 (ISSN) Fatehi, M ; Moghaddam, M ; Rahim, M ; Sharif University of Technology
    2012
    Abstract
    Purpose - The purpose of this paper is to present a novel approach in aeroservoelastic analysis and robust control of a wing section with two control surfaces in leading-edge and trailing-edge. The method demonstrates how the number of model uncertainties can affect the flutter margin. Design/methodology/approach - The proposed method effectively incorporates the structural model of a wing section with two degrees of freedom of pitch and plunge with two control surfaces on trailing and leading edges. A quasi-steady aerodynamics assumption is made for the aerodynamic modeling. Basically, perturbations are considered for the dynamic pressure models and uncertainty parameters are associated...