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    Collision Attacks on Hash Functions Using Linearization of Compress Function

    , M.Sc. Thesis Sharif University of Technology Kazemi, Ehsan (Author) ; 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... 

    Circulant matrix representation of PN-sequences with ideal autocorrelation property

    , Article IWCIT 2015 - Iran Workshop on Communication and Information Theory, 6 May 2015 through 7 May 2015 ; May , 2015 ; 9781479982356 (ISBN) Khojasteh, M. J ; Shoreh, M. H ; Salehi, J. A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    In this paper, we investigate PN-sequences with ideal autocorrelation property and the consequences of this property on the number of +1s and -1s and run structure of sequences. We begin by discussing and surveying about the length of PN-sequences with ideal autocorrelation property. From our discussion and survey we introduce circulant matrix representation of PN-sequence. Through circulant matrix representation we obtain system of non-linear equations that lead to ideal autocorrelation property. Rewriting PN-sequence and its autocorrelation property in {0,1} leads to a definition based on Hamming weight and Hamming distance and hence we can easily prove some results on the PN-sequences...