1,720,990 research outputs found
Countering Chosen-Ciphertext Attacks Against Noncommutative Polly Cracker-Type Cryptosystems
Full text linkIn [2], Stanislav Bulygin presents a chosen-ciphertext attack against certain instances of noncommutative polly cracker-type cryptosystems which were proposed in [7] and [9]. In this article, we present generalized versions of this attack, which can be used against virtually all polly cracker-type cryptosystems
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
More on linear hulls of PRESENT-like ciphers and a cryptanalysis of full-round EPCBC-96
Full text linkIn this paper we investigate the linear hull effect in the light-weight block cipher EPCBC. We give an efficient method of computing linear hulls with high capacity. We then apply found hulls to derive attacks on the full 32 rounds of EPCBC--96 and 20 rounds of EPCBC-48. Using the developed methods we revise the work of J.Y. Cho from 2010 and obtain an attack based on multidimensional linear approximations on 26 rounds of PRESENT--128. The results show that designers of block ciphers should take seriously the threat coming from the linear hull attacks and not just limit themselves to proving bounds based solely on linear characteristics
Algebraic cryptanalysis of the round-reduced and side channel analysis of the full PRINTCipher-48
Full text linkIn this paper we analyze the recently proposed light-weight block cipher PRINTCipher. Applying algebraic methods and SAT-solving we are able to break 8 rounds of PRINTCipher-48 with only 2 known plaintexts and 9 rounds under some additional assumptions. We show that it is possible to break the full 48-round cipher by assuming a moderate leakage of internal state bits or even just Hamming weights. Such a simulation side-channel attack has practical complexity. We investigate applicability of our method to cryptanalysis of the full PRINTCipher-48
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Abstract only
No full textThis book that represents the author's Ph.D. thesis is devoted to applying symbolic methods to the problems of decoding linear codes and of algebraic cryptanalysis. The paradigm we employ here is as follows. We reformulate the initial problem in terms of systems of polynomial equations over a finite field. The solution(s) of such systems should yield a way to solve the initial problem. Our main tools for handling polynomials and polynomial systems in such a paradigm is the technique of Gröbner bases and normal form reductions.
The first part of the book is devoted to formulating and solving specific polynomial systems that reduce the problem of decoding linear codes to the problem of polynomial system solving. We analyze the existing methods (mainly for the cyclic codes) and propose an original method for arbitrary linear codes that in some sense generalizes the Newton identities method widely known for cyclic codes. We investigate the structure of the underlying ideals andshow how one can solve the decoding problem -- both the so-called bounded decoding and more general nearest codeword decoding -- by finding reduced Gröbner bases of these ideals. The main feature of the method is that unlike usual methods based on Gröbner bases for "finite field" situations, we do not add the so-called field equations. This tremendously simplifies the underlying ideals, thus making feasible working with quite large parameters of codes. Further we address complexity issues, by giving some insight to the Macaulay matrix of the underlying systems. By making a series of assumptions we are able to provide an upper bound for the complexity coefficient of our method. We address also finding the minimum distance and the weight distribution. We provide solid experimental material and comparisons with some of the existing methods in this area.
In the second part we deal with the algebraic cryptanalysis of block iterative ciphers. Namely, we analyze the smallscale variants of the Advanced Encryption Standard (AES), which is a widely used modern block cipher. Here a cryptanalyst composes the polynomial systems which solutions should yield a secret key used by communicating parties in a symmetric cryptosystem. We analyze the systems formulated by researchers for the algebraic cryptanalysis, and identify the problem that conventional systems have many auxiliary variables that are not actually needed for the key recovery. Moreover, having many such auxiliary variables, specific to a given plaintext/ciphertext pair, complicates the use of several pairs which is common in cryptanalysis. We thus provide a new system where the auxiliary variables are eliminated via normal form reductions. The resulting system in key-variables only is then solved. We present experimental evidence that such an approach is quite good for small scaled ciphers. We investigate further our approach and employ the so-called meet-in-the-middle principle to see how far one can go in analyzing just 2--3 rounds of scaled ciphers. Additional "tuning techniques" are discussed together with experimental material. Overall, we believe that the material of this part of the thesis makes a step further in algebraic cryptanalysis of block ciphers.
A short description of the thesis is on the KLUDO webpage: http://kluedo.ub.uni-kl.de/volltexte/2009/2350/.</jats:p
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