# American Institute of Mathematical Sciences

May  2010, 4(2): 155-168. doi: 10.3934/amc.2010.4.155

## Explicit 2-power torsion of genus 2 curves over finite fields

 1 Departament de Matemàtica, Universitat de Lleida, Jaume II 69, Lleida 25001, Spain, Spain 2 Departament de Matemàtica Aplicada II, Universitat Politècnica de Catalunya, Jordi Girona 1–3, Barcelona 08134, Spain

Received  May 2009 Revised  March 2010 Published  May 2010

We give an efficient explicit algorithm to find the structure and generators of the maximal 2-subgroup of the Jacobian of a genus 2 curve over a finite field of odd characteristic. We use the 2-torsion points as seeds to successively perform a chain of halvings to find divisors of increasing 2-power order. The halving loop requires a solution to certain degree 16 polynomials over the base field, and the termination of the algorithm is based on the description of the graph structure of the maximal 2-subgroup. The structure of our algorithm is the natural extension of the even characteristic case.
Citation: Josep M. Miret, Jordi Pujolàs, Anna Rio. Explicit 2-power torsion of genus 2 curves over finite fields. Advances in Mathematics of Communications, 2010, 4 (2) : 155-168. doi: 10.3934/amc.2010.4.155
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