22,930 research outputs found
Formulas for p-th root computations in finite fields of characteristic p using polynomial basis
Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência da Computação, Florianópolis, 2016.Motivado por algoritmos criptográficos de emparelhamento bilinear, a computação da raiz cúbica em corpos finitos de característica 3 já fora abordada na literatura. Adicionalmente, novos estudos sobre a computação da raiz p-ésima em corpos finitos de característica p, onde p é um número primo, têm surgido. Estas contribuições estão centradas na computação de raízes para corpos de característica fixa ou para polinômios irredutíveis com poucos termos não nulos. Esta dissertação propõe novas famílias de polinômios irredutíveis em ??p, com k termos não nulos onde k = 2 e p = 3, para a computação eficiente da raiz p-ésima em corpos finitos de característica p. Além disso, para o caso onde p = 3, são obtidas novas extensões onde a computação da raiz cúbica é eficiente e polinômios cujo desempenho é ligeiramente melhor em comparação aos resultados da literatura. Palavras-chave: Criptografia, Teoria de Números, Aritmética em Corpos Finitos.Abstract : Efficient cube root computations in extensions fields of characteristic three have been studied, in part motivated by pairing cryptography implementations. Additionally, recent studies have emerged on the computation of p-th roots of finite fields of characteristic p, where p prime. These contributions have either considered a fixed characteristics for the extension field or irreducible polynomials with few nonzero terms. We provide new families of irreducible polynomials over ??p, taking into account polynomials with k = 2 nonzero terms and p = 3. Moreover, for the particular case p = 3, we slightly improve some previous results and we provide new extensions where efficient cube root computations are possible
A Point Counting Algorithm for Cyclic Covers of the Projective Line
We present a Kedlaya-style point counting algorithm for cyclic covers over a finite field with not dividing , and
and not necessarily coprime. This algorithm generalizes the
Gaudry-G\"urel algorithm for superelliptic curves to a more general class of
curves, and has essentially the same complexity. Our practical improvements
include a simplified algorithm exploiting the automorphism of ,
refined bounds on the -adic precision, and an alternative pseudo-basis for
the Monsky-Washnitzer cohomology which leads to an integral matrix when . Each of these improvements can also be applied to the original
Gaudry-G\"urel algorithm. We include some experimental results, applying our
algorithm to compute Weil polynomials of some large genus cyclic covers
Point compression for the trace zero subgroup over a small degree extension field
Using Semaev's summation polynomials, we derive a new equation for the
-rational points of the trace zero variety of an elliptic curve
defined over . Using this equation, we produce an optimal-size
representation for such points. Our representation is compatible with scalar
multiplication. We give a point compression algorithm to compute the
representation and a decompression algorithm to recover the original point (up
to some small ambiguity). The algorithms are efficient for trace zero varieties
coming from small degree extension fields. We give explicit equations and
discuss in detail the practically relevant cases of cubic and quintic field
extensions.Comment: 23 pages, to appear in Designs, Codes and Cryptograph
On Taking Square Roots without Quadratic Nonresidues over Finite Fields
We present a novel idea to compute square roots over finite fields, without
being given any quadratic nonresidue, and without assuming any unproven
hypothesis. The algorithm is deterministic and the proof is elementary. In some
cases, the square root algorithm runs in bit operations
over finite fields with elements. As an application, we construct a
deterministic primality proving algorithm, which runs in
for some integers .Comment: 14 page
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