Using modular polynomials for eta products to compute isogenies - Inria - Institut national de recherche en sciences et technologies du numérique
Pré-Publication, Document De Travail Année : 2024

Using modular polynomials for eta products to compute isogenies

Résumé

Let E be an elliptic curve over a field K and a prime. There exists an elliptic curve E * related to E by an isogeny of degree only if Φ (X, j(E)) = 0, where Φ (X, Y) is the traditional modular polynomial. Moreover, this polynomial gives the coefficients of E * , together with parameters needed to build the isogeny explicitly. Since the traditional modular polynomial has large coefficients, many families with smaller coefficients can be used instead, as described by Elkies, Atkin and others. In this work, we concentrate on the computation of modular polynomials for eta products, as considered by Fricke. We review and complete the properties of these eta products to be able to perform the computations of these polynomials using classical algorithms. We give algebraic formulas à la Atkin to compute the coefficients of E *. Numerical examples and comparisons to other families are also given.
Fichier principal
Vignette du fichier
etaproducts.pdf (328.84 Ko) Télécharger le fichier
Origine Fichiers produits par l'(les) auteur(s)

Dates et versions

hal-04423470 , version 1 (29-01-2024)

Licence

Identifiants

  • HAL Id : hal-04423470 , version 1

Citer

François Morain. Using modular polynomials for eta products to compute isogenies. 2024. ⟨hal-04423470⟩
75 Consultations
78 Téléchargements

Partager

More