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darkfi/script/research/ec/ordp.sage
2022-07-30 20:33:59 +02:00

95 lines
1.9 KiB
Python

from tabulate import tabulate
# This is a more usable version of valuate.sage, less instructional
# Return components for basis
def decomp(f, basis):
b0, b1, b2 = basis
a0, r = f.quo_rem(b0)
a1, r = r.quo_rem(b1)
a2, r = r.quo_rem(b2)
assert r == 0
return [a0, a1, a2]
def comp(comps, basis):
return sum(a*b for a, b in zip(comps, basis))
def apply_reduction(a, g, Ef, Eg):
assert a[2] == 0
a[0] = a[0]*Eg + a[1]*Ef
a[1] = 0
g[0] *= Eg
# EC_A, EC_B must be defined before calling this function
def ordp(P, original_f, debug=False):
EC = y^2 - x^3 - EC_A*x - EC_B
Px, Py = P
if Py != 0:
b0, b1, b2 = [(x - Px), (y - Py), 1]
# so we can replace (y - Py) with this
Ef = b0^2 + binomial(3,2)*Px*b0^1 + (3*Px^2 + EC_A)
Eg = (y + Py)
assert EC == b1*Eg - b0*Ef
else:
b0, b1, b2 = [y, x, 1]
# we can replace x with this
Ef = b0
Eg = x^2 + EC_A + EC_B
basis = [b0, b1, b2]
k = 0
a = [original_f, 0, 0]
g = [1]
table = []
table.append(("", "a", "g", "k"))
def log(step_name, a, g, k):
table.append((step_name, str(a), str(g), k))
log("start", a, g, k)
while True:
f = a[0]
a = decomp(f, basis)
log("decomp", a, g, k)
# Check remainder
if a[2] != 0:
break
# We can apply a reduction
k += 1
apply_reduction(a, g, Ef, Eg)
log("reduce", a, g, k)
if debug:
print(tabulate(table))
u = b0
f = comp(a, basis)
g = g[0]
assert u(Px, Py) == 0
assert f(Px, Py) != 0
assert g(Px, Py) != 0
if debug:
print(f"u = {u}")
print(f"f = {f}")
print(f"g = {g}")
return k
#K.<x, y> = GF(11)[]
#EC_A = 4
#EC_B = 0
#P = (2, 4)
#f = y - 2*x
#k = ordp(P, f, debug=True)
#print(f"k = {k}")