1,720,989 research outputs found
Abelian Varieties with Small Isogeny Class and Applications to Cryptography
Get PDFThesis (Ph.D.)--University of Washington, 2018An elliptic curve over a finite field \FF_q is called isolated if it admits few efficiently computable \FF_q-isogenies from to a non-isomorphic curve. We present a variation on the CM method that constructs isolated curves. Assuming the Bateman-Horn conjecture, we show that there is negligible probability that a curve of cryptographic size constructed via this method is vulnerable to any known attack on the ECDLP. A special case of isolated curves is when the \FF_q-isogeny class contains only one \FF_q-isomorphism class. We call an elliptic curve, or abelian variety, super-isolated if it has this property. We give a simple characterization of super-isolated elliptic curves, and several examples of cryptographic size. We prove that there are only super-isolated surfaces suitable for cryptographic use. Finally, we show that for any , there are only finitely many super-isolated ordinary simple abelian varities of genus . Essentially, we have an existence result in the practical range for genus , and a non-existence result for the impractical genera
P-adic analysis: a short course on recent work
No full textThis introduction to recent work in p-adic analysis and number theory will make accessible to a relatively general audience the efforts of a number of mathematicians over the last five years. After reviewing the basics (the construction of p-adic numbers and the p-adic analog of the complex number field, power series and Newton polygons), the author develops the properties of p-adic Dirichlet L-series using p-adic measures and integration. p-adic gamma functions are introduced, and their relationship to L-series is explored. Analogies with the corresponding complex analytic case are stressed
Abelian Varieties with Small Isogeny Class and Applications to Cryptography
No full textThesis (Ph.D.)--University of Washington, 2018An elliptic curve over a finite field \FF_q is called isolated if it admits few efficiently computable \FF_q-isogenies from to a non-isomorphic curve. We present a variation on the CM method that constructs isolated curves. Assuming the Bateman-Horn conjecture, we show that there is negligible probability that a curve of cryptographic size constructed via this method is vulnerable to any known attack on the ECDLP. A special case of isolated curves is when the \FF_q-isogeny class contains only one \FF_q-isomorphism class. We call an elliptic curve, or abelian variety, super-isolated if it has this property. We give a simple characterization of super-isolated elliptic curves, and several examples of cryptographic size. We prove that there are only super-isolated surfaces suitable for cryptographic use. Finally, we show that for any , there are only finitely many super-isolated ordinary simple abelian varities of genus . Essentially, we have an existence result in the practical range for genus , and a non-existence result for the impractical genera
Fast hashing on the Pentium
Get PDF© Springer-Vertag Berlin Heidelberg 1996. With the advent of the Pentium processor parallelization finally became available to Intel based computer systems. One of the design principles of the MD4-family of hash functions (MD4, MD5, SHA-1, RIPEMD-160) is to be fast on the 32-bit Intel processors. This paper shows that carefully coded implementations of these hash functions are able to exploit the Pentium’s superscalar architecture to its maximum effect: the performance with respect to execution on a non-parallel architecture increases by about 60%. This is an important result in view of the recent claims on the limited data bandwidth of these hash functions. Moreover, it is conjectured that these implementations are very close to optimal. It will also be shown that the performance penalty incurred by non-cached data and endianness conversion is limited, and in the order of 10% of running time.status: Publishe
Isolated Curves for Hyperelliptic Curve Cryptography
Get PDFThesis (Ph.D.)--University of Washington, 2012We introduce the notion of isolated genus two curves. There is no known efficient algorithm to explicitly construct isogenies between two genus two curves with large conductor gap. Thus there is no known way of transporting the discrete log problem (DLP) from an isolated curve to a large set of isogenous curves by constructing isogenies. Isolated genus two curves are curves that have large conductor gap to any other endomorphism classes. Isolated curves might be more secure for DLP based hyperelliptic curve cryptography. We establish results on explicit expressions for the index of an endomorphism ring in the maximal CM order, and give conditions under which the index is a prime number or an almost prime number for three different categories of quartic CM fields. We also derived heuristic asymptotic results on the densities and distributions of isolated genus two curves with CM by any fixed quartic CM field. Computational results, which are also shown for three explicit examples, agree with heuristic prediction with errors within a tolerable range
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
- …
