1,720,961 research outputs found
A new cost function for heuristic search of nonlinear substitutions
No full textThis work investigates the development of an improved cost function specifically designed for the rapid generation of highly nonlinear substitution or S-boxes, a key component in modern symmetric key ciphers. The S-boxes are generated via a tailored hill-climbing algorithm, a heuristic search method typically employed in solving complex computational problems. The novel cost function proposed in this paper is shown to expedite this generation process, reducing the iteration count by 25% relative to the best-known prior result, which required about 65,000 iterations. Furthermore, the approach enhances the likelihood of obtaining target S-boxes, with a threefold increase in successful outcomes compared to existing methods. Our method yields S-boxes that adhere to critical cryptographic measures, such as delta-uniformity, algebraic immunity, and others. This study emphasizes the specific application of the cost function to the generation of S-boxes, noting that its effectiveness may vary in other combinatorial optimization problems
Optimization of the PCF Cost Function for the Generation of Highly Nonlinear S-boxes
No full textCreation of reliable telecommunication communication channels providing confidential data, it is currently impossible to have reliable encryption algorithms. The most popular services that provide encryption algorithms include confidentiality, integrity, and authenticity services. Most modern symmetric encryption algorithms use nonlinear substitutions or abbreviated S-boxes. Their properties have a direct impact on the cryptographic strength of symmetric encryption. So, generating S-boxes with the right properties is certainly an important task for creating S-boxes. In this paper, we consider heuristic methods for generating nonlinear substitutions that use special cost functions (heuristics). During generation, the search algorithm changes the randomly generated substitution at each iteration and tries to reduce the value of the cost function. Search attempts are stopped either after finding the S-box with the desired properties, or after performing a certain number of iterations. Doubtless, the search efficiency depends on the chosen heuristic, namely, on the parameters of the cost function. In this paper, we consider the PCF cost function and optimize its parameters. We managed to optimize the parameters of this heuristic and achieve the least number of search iterations
Comparative Analysis of Cryptographic Hash Functions in Blockchain Systems
No full textIn the burgeoning realm of digital technologies, blockchain has emerged as a revolutionary force, underpinned by the intricate fabric of cryptographic hash functions. This study provides a comprehensive evaluation of various hash functions, delineating their processing efficacies across a spectrum of input block sizes. Through rigorous empirical analysis, our research juxtaposes the performance metrics of ten distinct algorithms, thereby offering invaluable insights into their respective computational robustness. Notably, our findings underscore the complexities inherent in the selection of an appropriate hash function for blockchain applications. Beyond mere processing speeds, the selection process requires a nuanced understanding of cryptographic resilience, adaptability to emerging threats, and seamless integration with prevailing infrastructures. While our results furnish a contemporaneous benchmark, they also accentuate the imperative for incessant research and adaptation in an ever-evolving digital landscape. This investigation serves both as a reference point for current blockchain applications and a clarion call for sustained innovation in the quest for optimized cryptographic solutions. The overarching aim is to fortify the blockchain's promise by ensuring its security and performance through the judicious application of cryptographic hash functions, thereby catalyzing a more decentralized, efficient, and secure digital future
Generation of Nonlinear Substitutions by Simulated Annealing Algorithm
No full textThe problem of nonlinear substitution generation (S-boxes) is investigated in many related works in symmetric key cryptography. In particular, the strength of symmetric ciphers to linear cryptanalysis is directly related to the nonlinearity of substitution. In addition to being highly nonlinear, S-boxes must be random, i.e., must not contain hidden mathematical constructs that facilitate algebraic cryptanalysis. The generation of such substitutions is a complex combinatorial optimization problem. Probabilistic algorithms are used to solve it, for instance the simulated annealing algorithm, which is well-fitted to a discrete search space. We propose a new cost function based on Walsh–Hadamard spectrum computation, and investigate the search efficiency of S-boxes using a simulated annealing algorithm. For this purpose, we conduct numerous experiments with different input parameters: initial temperature, cooling coefficient, number of internal and external loops. As the results of the research show, applying the new cost function allows for the rapid generation of nonlinear substitutions. To find 8-bit bijective S-boxes with nonlinearity 104, we need about 83,000 iterations. At the same time, the probability of finding the target result is 100%
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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