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Ciphertext-only attack on d × d Hill in O(d13d)
, Article Information Processing Letters ; Volume 118 , 2017 , Pages 25-29 ; 00200190 (ISSN) ; Ahmadi, S ; Sharif University of Technology
Elsevier B.V
2017
Abstract
Hill is a classical cipher which is generally believed to be resistant against ciphertext-only attack. In this paper, by using a divide-and-conquer technique, it is first shown that Hill with d×d key matrix over Z26 can be broken with computational complexity of O(d26d), for the English language. This is much less than the only publicly known attack, i.e., the brute-force with complexity of O(d326d2). Then by using the Chinese Remainder Theorem, it is shown that the computational complexity of the proposed attack can be reduced down to O(d13d). Using an information-theoretic approach, it is shown that the minimum ciphertext length required for a successful attack increases by a factor of...
Efficient fully format compliant selective scrambling methods for compressed video streams
, Article Advanced International Conference on Telecommunications andInternational Conference on Internet and Web Applications and Services, AICT/ICIW'06, Guadelope, 19 February 2006 through 25 February 2006 ; Volume 2006 , 2006 , Pages 42- ; 0769525229 (ISBN); 9780769525228 (ISBN) ; Ghaemmaghami, S ; Khazaei, S ; Sharif University of Technology
2006
Abstract
Format compliance, a desirable feature of multimedia security systems, means that the secured bitstream resembles the unprotected compressed bitstream. It is called full format compliance, if the scrambled stream can be decoded by a typical decoder. In this paper, we address the issues that are to be carefully taken into account to develop efficient fully format compliant scrambling methods for compressed video. We also propose new selective scrambling methods for securing compressed video streams. The security issues, in different parts of these scrambling methods, are analyzed and their impact on bit-rate and complexity is discussed. We show that our scrambling methods provide...
Relationship of profitability of world’s top companies with entrepreneurship, competitiveness, and business environment indicators
, Article Applied Economics ; Volume 53, Issue 23 , December , 2020 , Pages 2584-2597 ; Sharif University of Technology
Routledge
2020
Abstract
Identifying the factors affecting profitability is important from the perspective of market players. One of the most important benchmarks of firm performance is accounting profit and effective factors analysis so that users of accounting information analyse the factors affecting profit, firm performance and various aspects of its performance and according to estimates Done, make your own decision on how to allocate resources. The main purpose of this study is to investigate the impact of some factors of competitiveness, entrepreneurship and business environment indicators on the profitability of the world’s top companies. For this purpose, 176 top companies in the world from 2013 to 2018...
Relationship of profitability of world’s top companies with entrepreneurship, competitiveness, and business environment indicators
, Article Applied Economics ; Volume 53, Issue 23 , 2021 , Pages 2584-2597 ; 00036846 (ISSN) ; Sharif University of Technology
Routledge
2021
Abstract
Identifying the factors affecting profitability is important from the perspective of market players. One of the most important benchmarks of firm performance is accounting profit and effective factors analysis so that users of accounting information analyse the factors affecting profit, firm performance and various aspects of its performance and according to estimates Done, make your own decision on how to allocate resources. The main purpose of this study is to investigate the impact of some factors of competitiveness, entrepreneurship and business environment indicators on the profitability of the world’s top companies. For this purpose, 176 top companies in the world from 2013 to 2018...
Breaking anonymity of some recent lightweight RFID authentication protocols
, Article Wireless Networks ; Volume 25, Issue 3 , 2018 , Pages 1-18 ; 10220038 (ISSN) ; Abdolmaleki, B ; Khazaei, S ; Aref, M. R ; Sharif University of Technology
Springer New York LLC
2018
Abstract
Due to their impressive advantages, Radio Frequency IDentification (RFID) systems are ubiquitously found in various novel applications. These applications are usually in need of quick and accurate authentication or identification. In many cases, it has been shown that if such systems are not properly designed, an adversary can cause security and privacy concerns for end-users. In order to deal with these concerns, impressive endeavors have been made which have resulted in various RFID authentications being proposed. In this study, we analyze three lightweight RFID authentication protocols proposed in Wireless Personal Communications (2014), Computers & Security (2015) and Wireless Networks...
Breaking anonymity of some recent lightweight RFID authentication protocols
, Article Wireless Networks ; Volume 25, Issue 3 , 2019 , Pages 1235-1252 ; 10220038 (ISSN) ; Abdolmaleki, B ; Khazaei, S ; Aref, M. R ; Sharif University of Technology
Springer New York LLC
2019
Abstract
Due to their impressive advantages, Radio Frequency IDentification (RFID) systems are ubiquitously found in various novel applications. These applications are usually in need of quick and accurate authentication or identification. In many cases, it has been shown that if such systems are not properly designed, an adversary can cause security and privacy concerns for end-users. In order to deal with these concerns, impressive endeavors have been made which have resulted in various RFID authentications being proposed. In this study, we analyze three lightweight RFID authentication protocols proposed in Wireless Personal Communications (2014), Computers & Security (2015) and Wireless Networks...
Game-based privacy analysis of RFID security schemes for confident authentication in IoT
, Article Wireless Personal Communications ; Volume 95, Issue 4 , 2017 , Pages 5057-5080 ; 09296212 (ISSN) ; Baghery, K ; Khazaei, S ; Aref, M. R ; Sharif University of Technology
2017
Abstract
Recently, Radio Frequency Identification (RFID) and Near Field Communication systems are found in various user-friendly services that all of us deal with in our daily lives. As these systems are ubiquitously deployed in different authentication and identification applications, inferring information about our behavior will be possible by monitoring our use of them. In order to provide privacy and security requirements of RFID users in novel authentication applications, lots of security schemes have been proposed which have tried to provide secure and untraceable communication for end-users. In this paper, we investigate the privacy of three RFID security schemes which have been proposed...
A high-accuracy hybrid method for short-term wind power forecasting
, Article Energy ; Volume 238 , 2022 ; 03605442 (ISSN) ; Ehsan, M ; Soleymani, S ; Mohammadnezhad Shourkaei, H ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
In this article, a high-accuracy hybrid approach for short-term wind power forecasting is proposed using historical data of wind farm and Numerical Weather Prediction (NWP) data. The power forecasting is carried out in three stages: wind direction forecasting, wind speed forecasting, and wind power forecasting. In all three phases, the same hybrid method is used, and the only difference is in the input data set. The main steps of the proposed method are constituted of outlier detection, decomposition of time series using wavelet transform, effective feature selection and prediction of each time series decomposed using Multilayer Perceptron (MLP) neural network. The combination of automatic...
Effect of long-range correlated disorder on the transverse localization of light in 1D array of optical waveguides
, Article Optics Communications ; Volume 307 , 2013 , Pages 39-45 ; 00304018 (ISSN) ; Mahdavi, S. M ; Bahrampour, A. R ; Golshani, M ; Sharif University of Technology
2013
Abstract
In this paper, the effects of the long-range correlated diagonal disordered optical waveguide arrays in the presence and absence of the positive Kerr nonlinearity are analyzed numerically. The calculated inverse localization length shows that the long-range correlation in a disordered system causes a decrease in the transverse localization in linear optical waveguide arrays. In the presence of positive Kerr nonlinearity, the inverse localization length is increased by increasing the nonlinear parameters in long-range correlated disordered systems in comparison with the uniform distribution disordered systems. This means that the long range correlation causes an enhancement of transverse...
Effect of Kerr nonlinearity on the transverse localization of light in 1D array of optical waveguides with off-diagonal disorder
, Article Optics Communications ; Volume 294 , 2013 , Pages 299-304 ; 00304018 (ISSN) ; Golshani, M ; Bahrampour, A. R ; Mahdavi, S. M ; Sharif University of Technology
2013
Abstract
In this paper a simulation of the transverse localization of light in 1D array of optical waveguides in the presence of off-diagonal disorder is presented. Effects of self-focusing and self-defocusing Kerr nonlinearity on the transverse localization of surface and bulk modes of the disordered waveguides array are taken into consideration. The simulation shows that in the off-diagonal disordered array at low nonlinear parameters, the transverse localization of light becomes more than that of the corresponding diagonal disordered array. However by increasing the nonlinear parameters the diagonal disordered array is localized more than the associated off-diagonal disordered array for both...
Poly(vinyl alcohol)/graphene oxide mixed matrix membranes for pervaporation of toluene and isooctane
, Article Polymer - Plastics Technology and Engineering ; Volume 56, Issue 12 , 2017 , Pages 1286-1294 ; 03602559 (ISSN) ; Mohebbi, V ; Behbahani, R. M ; Ahmad Ramazani, S. A ; Sharif University of Technology
2017
Abstract
Poly(vinyl alcohol)/graphene oxide mixed matrix membranes have been prepared and applied for the pervaporation of isooctane (aliphatic) and toluene (aromatic) mixtures. Characteristics of the membranes such as crystallinity, morphology, and swelling have been investigated, and the results have been used to describe pervaporation performance. Experimental tests evidenced that incorporation of low content of graphene oxide nanoplates (0.5 wt%) in poly(vinyl alcohol) increases affinity of the membrane to aromatics by S and π bonds and selectivity increase to about four times. Moreover, interaction of graphene oxide with toluene results in increasing of swelling and decreasing of permeation...
Pervaporation of toluene and iso-octane through poly(vinyl alcohol)/graphene oxide nanoplate mixed matrix membranes: Comparison of crosslinked and noncrosslinked membranes
, Article Journal of Applied Polymer Science ; Volume 135, Issue 7 , 2018 ; 00218995 (ISSN) ; Mohebbi, V ; Behbahani, R. M ; Ramazani S. A., A ; Sharif University of Technology
John Wiley and Sons Inc
2018
Abstract
Removal of aromatic compounds from fuel is an essential requirement in new environmental policies. In the present study, poly(vinyl alcohol)/graphene oxide (GO) mixed matrix membranes were prepared and applied to the separation of toluene from iso-octane by pervaporation, considering the similarity and interaction between graphene and aromatics. The effects of crosslinking and GO content on separation efficiency have been investigated in detail. Owing to the high affinity of GO with toluene through s and π bonds, the selectivity of the membranes was increased by incorporating a low amount of GO. The results also indicated that noncrosslinked membranes have higher selectivity and permeation...
On ideal homomorphic secret sharing schemes and their decomposition
, Article Designs, Codes, and Cryptography ; Volume 89, Issue 9 , 2021 , Pages 2079-2096 ; 09251022 (ISSN) ; Kaboli, R ; Khazaei, S ; Parviz, M ; Rafiei, M. M ; Sharif University of Technology
Springer
2021
Abstract
In 1992, Frankel and Desmedt introduced a technique that enables one to reduce the secret space of an ideal homomorphic secret sharing scheme (IHSSS) into any of its characteristic subgroups. In this paper, we propose a similar technique to reduce the secret space of IHSSSs called the quotient technique. By using the quotient technique, we show that it is possible to yield an ideal linear scheme from an IHSSS for the same access structure, providing an alternative proof of a recent result by Jafari and Khazaei. Moreover, we introduce the concept of decomposition of secret sharing schemes. We give a decomposition for IHSSSs, and as an application, we present a necessary and sufficient...
On The Behavior of Low-Rise, Irregular, Dual Structures
, M.Sc. Thesis Sharif University of Technology ; Mofid, Masoud (Supervisor)
Abstract
The Response modification factor R represents the behavior of the structure such as ductility, overstrength and the inherent redundancy. This factor shall be defined according to the type of lateral force resisting system. However, there are some complexities and/or uncertainties in codes related to the R factor according to the height, form of irregularities and structural systems. Therefore, from the scientific point of view as well as reliability, it is very clear that the R factor cannot be similar for all kinds of structures, categorized as a specific group. In this investigation, assuming a low-rise, vertically irregular structure with a heliport which has a dual structural system...
Modeling and Optimization of Composite Brake Friction Materials Formulation
, M.Sc. Thesis Sharif University of Technology ; Shojaei, Akbar (Supervisor)
Abstract
Automotive brake pad is one of the most widely used composites. Commonly, more than 10 components are applied to make these materials and due to the large number of components and interactions between them, choice, explaination of the behavior and optimization of brake friction materials are some industry's challenges. Until now, some methods have been presented to design and optimization of these materials, but due to different complexities, there is lack of practical method that could be used for explaining the tribological behavior, engineering calculation and optimization of brake friction materials. Today, formulation of the current brake pads in the industry has mainly come from trial...
Reflection Cryptanalysis of GOST Block Cipher
,
M.Sc. Thesis
Sharif University of Technology
;
khazaei, Shahram
(Supervisor)
Abstract
Block ciphers are the central tool in the design of security protocols. GOST is a block cipher that several attacks have been published on it during the past 20 years. One of them is the reflection attack that was first introduced in 2007. This attack utilizes similarities of some round functions of both encryption and decryption processes. In addition, there are approaches that combines techniques of the reflection attack and variants of the meet-in-the-middle attack. In this thesis, we study reflection-based attacks on GOST. We first describe the GOST block cipher and the reflection attack. Then, we review previous reflectionbased attacks such as reflection-meet-in-the-middle attack and...
Linear-Differential Cryptanalysis of Word-Reduced Variants of Cubehash
, M.Sc. Thesis Sharif University of Technology ; Khazaei, Shahram (Supervisor)
Abstract
In this thesis, first we will have a brief review on hash functions and related concepts.Then, we will descibe the hash function, Cubehash, which is one of the competitors in the competition held by NIST for selecting SHA-3 standard. Next, we will describe an attack based on linearization of differential paths in hash functions and apply this attack on Cubehash. At the end, we will discuss the results of this attack on Cubehash
Cryptographic Hash Functions from Expander Graphs
, M.Sc. Thesis Sharif University of Technology ; khazaei, Shahram (Supervisor)
Abstract
A hash function maps efficiently every finite length string to a fixed one. The output represents the entire content of the input, similar to digital fingerprint of input text. In order to be able to use a hash function in cryptography, it should be hard to find two distinct inputs with the same output (collision), because finding a collision in hash functions leads to malicious attacks on many security systems.We say a hash function is provably collision resistant, if finding a collision can be reduced to the known hard problems. Family of MD hash functions are one of the most famous applied hash functions which are considerably used in industrial applications. However, they are not...
Multiple human tracking using PHD filter in distributed camera network
, Article Proceedings of the 4th International Conference on Computer and Knowledge Engineering, ICCKE 2014 ; 2014 , pp. 569-574 ; ISBN: 9781479954865 ; Jamzad, M ; Sharif University of Technology
2014
Abstract
The Gaussian mixture probability hypothesis density (GM-PHD) filter is a closed form approximation of the multi-target Bayes filter which can overcome most multitarget tracking problems. Limited field of view, decreasing cost of cameras, and advances of using multi-camera induce us to use large-scale camera networks. In this paper, a multihuman tracking framework using the PHD filter in a distributed camera network is proposed. Each camera tracks objects locally with PHD filter and a track-after-detect scheme and its estimates of targets are sent to neighboring nodes. Then each camera fuses its local estimates with it's neighbors. The proposed method is evaluated on the public PETS2009...
Randomized partial checking revisited
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) ; Volume 7779 LNCS , February , 2013 , Pages 115-128 ; 03029743 (ISSN) ; 9783642360947 (ISBN) ; Wikstrom, D ; Sharif University of Technology
2013
Abstract
We study mix-nets with randomized partial checking (RPC) as proposed by Jakobsson, Juels, and Rivest (2002). RPC is a technique to verify the correctness of an execution both for Chaumian and homomorphic mix-nets. The idea is to relax the correctness and privacy requirements to achieve a more efficient mix-net. We identify serious issues in the original description of mix-nets with RPC and show how to exploit these to break both correctness and privacy, both for Chaumian and homomorphic mix-nets. Our attacks are practical and applicable to real world mix-net implementations, e.g., the Civitas and the Scantegrity voting systems