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Collision Attacks on Hash Functions Using Linearization of Compress Function
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor) ; Eghlidos, Taraneh (Supervisor)
Abstract
Collision attack is one of the usual attacks in cryptanalysis of hash functions. One method for applying this attack is linear approximation of equivalent compress function. Finding collisions for linearized compress function, having low Hamming weight, with a large probability could provide collisions for the main compress function. For this purpose, the problem of finding collision for used compress function is modeled by that of the linearized one, having low Hamming weight differences with a large probability. The problem of finding collisions with low Hamming weight differences is equivalent to the problem of finding codewords with low Hamming weights in linear binary code. Canteaut and...
Application of Karnaugh map for easy generation of error correcting codes
, Article Scientia Iranica ; Volume 19, Issue 3 , June , 2012 , Pages 690-695 ; 10263098 (ISSN) ; Sharif University of Technology
2012
Abstract
With increasing use of data transmission between digital systems as well as subsystems, the need for more reliable communication is felt. In this research, a new approach to the linear error correcting codes is introduced. Among advantages of this technique are simpler code construction and also decoding algorithm, as well as easier understanding of the basic concept. Based on an earlier paper and also recent work done, we first discuss briefly the use of Karnaugh map and its advantages in constructing simple codes. We then prove a theorem on application of the map to multiple error correcting codes. Using these results, we propose a simple technique that leads to obtaining a code with more...
Linear decoupled and quasi-decoupled space-time codes
, Article IEEE Transactions on Communications ; Volume 55, Issue 1 , 2007 , Pages 54-59 ; 00906778 (ISSN) ; Khalaj, B. H ; Shamsi, M ; Sharif University of Technology
2007
Abstract
Space-time transmit diversity results in coupling of transmitted symbols across different antennas, which increases the complexity of maximum-likelihood decoding. Symbol coupling can be completely or partially avoided if the space-time code (STC) satisfies specific decoupling conditions; examples of such codes are orthogonal space-time block codes and quasi-orthogonal codes. In this letter, we study decoupling conditions for a linear full-diversity STC. Quasi-decoupled codes are proposed as a partially decoupled full-diversity STC of any rate for any number of transmit antennas with minimum decoding delay. By optimizing the coding gain of quasi-decoupled codes, it is shown that...
Decoding Graph based Linear Codes Using Deep Neural Networks
, M.Sc. Thesis Sharif University of Technology ; Amini, Arash (Supervisor) ; Saleh Kaleybar, Saber (Supervisor)
Abstract
One of the most important goals we pursue in telecommunications science is to send and receive information from telecommunication channels. By designing a powerful telecommunication system consisting of a transmitter and a receiver, we achieve this goal. Speed of data transmission, accuracy of received information and speed of data extraction are some of the criteria by which the performance of a telecommunication system can be evaluated. No telecommunication channel is free of noise. For this reason, additional information is added to the original information in the transmitter, which can still be extracted if the original information is noisy. This process is called coding. Following...
Capacity achieving linear codes with random binary sparse generating matrices over the binary symmetric channel
, Article IEEE International Symposium on Information Theory - Proceedings ; 2012 , Pages 621-625 ; 9781467325790 (ISBN) ; Abadi, H. K ; Pad, P ; Saeedi, H ; Marvasti, F ; Alishahi, K ; Sharif University of Technology
IEEE
2012
Abstract
In this paper, we prove the existence of capacity achieving linear codes with random binary sparse generating matrices over the Binary Symmetric Channel (BSC). The results on the existence of capacity achieving linear codes in the literature are limited to the random binary codes with equal probability generating matrix elements and sparse parity-check matrices. Moreover, the codes with sparse generating matrices reported in the literature are not proved to be capacity achieving for channels other than Binary Erasure Channel. As opposed to the existing results in the literature, which are based on optimal maximum a posteriori decoders, the proposed approach is based on a different decoder...
Transmission of non-linear binary input functions over a CDMA system
, Article IEEE International Symposium on Information Theory - Proceedings, 1 July 2012 through 6 July 2012 ; July , 2012 , Pages 1401-1405 ; 9781467325790 (ISBN) ; Gohari, A ; Aghaeinia, H ; Sharif University of Technology
2012
Abstract
We study the problem of transmission of binary input non-linear functions over a network of mobiles based on CDMA. Motivation for this study comes from the application of using cheap measurement devices installed on personal cellphones to monitor environmental parameters such as air pollution, temperature and noise level. Our model resembles the MAC model of Nazer and Gastpar except that the encoders are restricted to be CDMA encoders. Unlike the work of Nazer and Gastpar whose main attention is transmission of linear functions, we deal with non-linear functions with binary inputs. A main contribution of this paper is a lower bound on the computational capacity for this problem. While in the...
Multi variable-layer neural networks for decoding linear codes
, Article 2020 Iran Workshop on Communication and Information Theory, IWCIT 2020, 26 May 2020 through 28 May 2020 ; August , 2020 ; Salehkaleybar, S ; Amini, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
The belief propagation algorithm is a state of the art decoding technique for a variety of linear codes such as LDPC codes. The iterative structure of this algorithm is reminiscent of a neural network with multiple layers. Indeed, this similarity has been recently exploited to improve the decoding performance by tuning the weights of the equivalent neural network. In this paper, we introduce a new network architecture by increasing the number of variable-node layers, while keeping the check-node layers unchanged. The changes are applied in a manner that the decoding performance of the network becomes independent of the transmitted codeword; hence, a training stage with only the all-zero...
Capacity of network coding for wireless multicasting
, Article IEEE Wireless and Microwave Technology Conference, WAMICON 2006, Clearwater Beach, FL, 4 December 2006 through 5 December 2006 ; 2006 ; 1424408482 (ISBN); 9781424408481 (ISBN) ; Khalaj, B. H ; Sharif University of Technology
2006
Abstract
In this paper, we consider the network coding in networks with broadcast channels (called hypernetworks) as the first step for applying network coding to wireless networks. We first prove a Max-Flow Min-Cut theorem for such networks. While we propose an algorithm to achieve this bound, we will introduce new definitions and provide sufficient tools to extend many of the theorems stated for flows in wireline networks to the case of hypernetworks. As an example, we will extend the Max-Flow Min-Cut condition for feasibility of the point-to-point connection in wireline networks to the case of hypernetworks. Then, we will extend the algebraic approach of Koetter and Medard in [3] to the...
Wireless multicasting using network coding
, Article 2006 1st Workshop on Operator-Assisted (Wireless-Mesh) Community Networks, OpComm 2006, Berlin, 18 September 2006 through 19 September 2006 ; 2006 ; 1424406927 (ISBN); 9781424406920 (ISBN) ; Khalaj, B. H ; Sharif University of Technology
2006
Abstract
In this paper, we consider the network coding in networks with broadcast channels (called hypernetworks) as the first step for applying network coding to wireless networks. We first prove a Max-Flow Min-Cut theorem for such networks. While we propose an algorithm to achieve this bound, we will introduce new definitions and provide sufficient tools to extend many of the theorems stated for flows in wireline networks to the case of hypernetworks. As an example, we will extend the Max-Flow Min-Cut condition for feasibility of the point-to-point connection in wireline networks to the case of hypernetworks. Then, we will extend the algebraic approach of Koetter and Medard in [3] to the...