The 2-Adic CM Method for Genus 2 Curves with Application to Cryptography

  • P. Gaudry
  • T. Houtmann
  • D. Kohel
  • C. Ritzenthaler
  • A. Weng
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4284)


The complex multiplication (CM) method for genus 2 is currently the most efficient way of generating genus 2 hyperelliptic curves defined over large prime fields and suitable for cryptography. Since low class number might be seen as a potential threat, it is of interest to push the method as far as possible. We have thus designed a new algorithm for the construction of CM invariants of genus 2 curves, using 2-adic lifting of an input curve over a small finite field. This provides a numerically stable alternative to the complex analytic method in the first phase of the CM method for genus 2. As an example we compute an irreducible factor of the Igusa class polynomial system for the quartic CM field ℚ \((i\sqrt{75 + 12\sqrt{17}})\), whose class number is 50. We also introduce a new representation to describe the CM curves: a set of polynomials in (j 1,j 2,j 3) which vanish on the precise set of triples which are the Igusa invariants of curves whose Jacobians have CM by a prescribed field. The new representation provides a speedup in the second phase, which uses Mestre’s algorithm to construct a genus 2 Jacobian of prime order over a large prime field for use in cryptography.


Elliptic Curf Isomorphism Class Abelian Variety Class Number Minimal Polynomial 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2006

Authors and Affiliations

  • P. Gaudry
    • 1
    • 2
  • T. Houtmann
    • 2
  • D. Kohel
    • 3
  • C. Ritzenthaler
    • 4
  • A. Weng
    • 2
  1. 1.LORIA – Projet SPACESVandoeuvre-lès-Nancy CedexFrance
  2. 2.Laboratoire d’Informatique (LIX), École polytechniquePalaiseau CedexFrance
  3. 3.School of Mathematics and StatisticsThe University of SydneyAustralia
  4. 4.Institut de Mathématiques de LuminyMarseille Cedex 9France

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