simonmasson / efficient-glv-curves-generation

Generation of efficient four-dimensional GLV curves with high security (256-bit)

Efficient GLV curves generation

Generation of efficient four-dimensional GLV curves with high security (256-bit)

How to use ?

sage : load('generating_curves.sage')
NB : if you want to use other primes, just change the line 84 of generating_curves.sage with primes = [my, new, primes].

Files description

• auxiliary_functions.sage
  separate_square_factors(r) returns s and D such that r = s^2D with s rational and D square-free.
  roots_d2(P) returns the roots of a degree 2 polynomial.
  get_hasegawa_j_inv(d) returns the j-invariant of a Hasegawa Q-curve of degree d.
  get_hasegawa_reduction_coefficients(p, d, s, D) returns A and B in GF(p^2) defining the Hasegawa curve y^2 = x^3 + Ax + B parametrized by s, d and Delta.

• CM_Q-curves.sage
  contruct_Discs_D0_f return the list of possible discriminants for a CM Q-curve with deg(H_D) = 1 or 2.
  construct_CM_j_roots returns the possible j-invariants for a CM Q-curve with deg(H_D) = 1 or 2.

• Hase_CM_curves.sage
  get_Qfamily_equation_from_j(d, j0) returns the equation satisfied by (s, Delta) to get j(d, s, Delta) = j0.
  compute_Hase_CM_curves.sage returns the list of (d, s, Delta) for which a CM Q-curve of degree d arises.

• generating_primes.sage
  Computes a list of 256-bit primes with efficient finite field arithmetic, and stores it in a file primes.sage.

• generating_curves.sage
  get_possible_traces(p, Delta) returns the list of the twisted curves traces for a given quadratic finite field F_{p^2} and a given endomorphisms algebra Q(√Δ).
  get_curve_order_and_twist_orders(P, Q1, traces) (Q1 = [p]P) return [a, L] where a is the order of the curve, and L is the list of the twisted curves orders.
  write_curve(cpt, file, p, A, B, order, N, twist_orders, E, d, s, D) write a new curve in file, for which there is an efficient arithmetic, and for which we can apply the four-dimensional GLV method. The list is stored in GLV4_curves.sage.

• primes.sage
  File created by generating_primes.sage.

• GLV4_curves.sage
  File created by generating_curves.sage. Each element of the list represents a curve, given in the form : [p, A, B, order, N, [twists], Delta, d, s, D] where the curve is given by E_{d, s, D} : y^2 = x^3 + A*x + B with A,B in F_{p^2} = F_p(sqrt(Delta)), #E = order, N|#E is prime, and [twists] are the orders of the twists.