Halving for the 2-Sylow subgroup of genus 2 curves over binary fields

  • Authors:
  • J. M. Miret;R. Moreno;J. PujolàS;A. Rio

  • Affiliations:
  • Dept. de Matemàtica, Universitat de Lleida, Jaume II 69, 25001 Lleida, Spain;Dept. de Matemàtica, Universitat de Lleida, Jaume II 69, 25001 Lleida, Spain;Dept. de Matemàtica, Universitat de Lleida, Jaume II 69, 25001 Lleida, Spain;Dept. de Matemàtica Aplicada II, Universitat Politècnica de Catalunya, Jordi Girona 1--3, Barcelona, Spain

  • Venue:
  • Finite Fields and Their Applications
  • Year:
  • 2009

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Abstract

We give a deterministic polynomial time algorithm to find the structure of the 2-Sylow subgroup of the Jacobian of a genus 2 curve over a finite field of characteristic 2. Our procedure starts with the points of order 2 and then performs a chain of successive halvings while such an operation makes sense. The stopping condition is triggered when certain polynomials fail to have roots in the base field, as previously shown by I. Kitamura, M. Katagi and T. Takagi. The structure of our algorithm is similar to the already known case of genus 1 and odd characteristic.