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276 lines
9.6 KiB
Python
276 lines
9.6 KiB
Python
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# Prover implementation for Weierstrass curves of the form
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# y^2 = x^3 + A * x + B, specifically with a = 0 and b = 7, with group laws
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# operating on affine and Jacobian coordinates, including the point at infinity
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# represented by a 4th variable in coordinates.
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load("group_prover.sage")
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class affinepoint:
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def __init__(self, x, y, infinity=0):
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self.x = x
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self.y = y
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self.infinity = infinity
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def __str__(self):
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return "affinepoint(x=%s,y=%s,inf=%s)" % (self.x, self.y, self.infinity)
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class jacobianpoint:
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def __init__(self, x, y, z, infinity=0):
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self.X = x
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self.Y = y
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self.Z = z
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self.Infinity = infinity
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def __str__(self):
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return "jacobianpoint(X=%s,Y=%s,Z=%s,inf=%s)" % (self.X, self.Y, self.Z, self.Infinity)
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def point_at_infinity():
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return jacobianpoint(1, 1, 1, 1)
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def negate(p):
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if p.__class__ == affinepoint:
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return affinepoint(p.x, -p.y)
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if p.__class__ == jacobianpoint:
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return jacobianpoint(p.X, -p.Y, p.Z)
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assert(False)
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def on_weierstrass_curve(A, B, p):
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"""Return a set of zero-expressions for an affine point to be on the curve"""
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return constraints(zero={p.x^3 + A*p.x + B - p.y^2: 'on_curve'})
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def tangential_to_weierstrass_curve(A, B, p12, p3):
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"""Return a set of zero-expressions for ((x12,y12),(x3,y3)) to be a line that is tangential to the curve at (x12,y12)"""
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return constraints(zero={
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(p12.y - p3.y) * (p12.y * 2) - (p12.x^2 * 3 + A) * (p12.x - p3.x): 'tangential_to_curve'
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})
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def colinear(p1, p2, p3):
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"""Return a set of zero-expressions for ((x1,y1),(x2,y2),(x3,y3)) to be collinear"""
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return constraints(zero={
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(p1.y - p2.y) * (p1.x - p3.x) - (p1.y - p3.y) * (p1.x - p2.x): 'colinear_1',
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(p2.y - p3.y) * (p2.x - p1.x) - (p2.y - p1.y) * (p2.x - p3.x): 'colinear_2',
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(p3.y - p1.y) * (p3.x - p2.x) - (p3.y - p2.y) * (p3.x - p1.x): 'colinear_3'
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})
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def good_affine_point(p):
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return constraints(nonzero={p.x : 'nonzero_x', p.y : 'nonzero_y'})
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def good_jacobian_point(p):
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return constraints(nonzero={p.X : 'nonzero_X', p.Y : 'nonzero_Y', p.Z^6 : 'nonzero_Z'})
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def good_point(p):
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return constraints(nonzero={p.Z^6 : 'nonzero_X'})
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def finite(p, *affine_fns):
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con = good_point(p) + constraints(zero={p.Infinity : 'finite_point'})
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if p.Z != 0:
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return con + reduce(lambda a, b: a + b, (f(affinepoint(p.X / p.Z^2, p.Y / p.Z^3)) for f in affine_fns), con)
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else:
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return con
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def infinite(p):
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return constraints(nonzero={p.Infinity : 'infinite_point'})
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def law_jacobian_weierstrass_add(A, B, pa, pb, pA, pB, pC):
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"""Check whether the passed set of coordinates is a valid Jacobian add, given assumptions"""
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assumeLaw = (good_affine_point(pa) +
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good_affine_point(pb) +
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good_jacobian_point(pA) +
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good_jacobian_point(pB) +
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on_weierstrass_curve(A, B, pa) +
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on_weierstrass_curve(A, B, pb) +
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finite(pA) +
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finite(pB) +
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constraints(nonzero={pa.x - pb.x : 'different_x'}))
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require = (finite(pC, lambda pc: on_weierstrass_curve(A, B, pc) +
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colinear(pa, pb, negate(pc))))
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return (assumeLaw, require)
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def law_jacobian_weierstrass_double(A, B, pa, pb, pA, pB, pC):
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"""Check whether the passed set of coordinates is a valid Jacobian doubling, given assumptions"""
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assumeLaw = (good_affine_point(pa) +
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good_affine_point(pb) +
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good_jacobian_point(pA) +
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good_jacobian_point(pB) +
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on_weierstrass_curve(A, B, pa) +
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on_weierstrass_curve(A, B, pb) +
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finite(pA) +
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finite(pB) +
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constraints(zero={pa.x - pb.x : 'equal_x', pa.y - pb.y : 'equal_y'}))
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require = (finite(pC, lambda pc: on_weierstrass_curve(A, B, pc) +
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tangential_to_weierstrass_curve(A, B, pa, negate(pc))))
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return (assumeLaw, require)
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def law_jacobian_weierstrass_add_opposites(A, B, pa, pb, pA, pB, pC):
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assumeLaw = (good_affine_point(pa) +
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good_affine_point(pb) +
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good_jacobian_point(pA) +
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good_jacobian_point(pB) +
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on_weierstrass_curve(A, B, pa) +
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on_weierstrass_curve(A, B, pb) +
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finite(pA) +
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finite(pB) +
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constraints(zero={pa.x - pb.x : 'equal_x', pa.y + pb.y : 'opposite_y'}))
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require = infinite(pC)
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return (assumeLaw, require)
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def law_jacobian_weierstrass_add_infinite_a(A, B, pa, pb, pA, pB, pC):
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assumeLaw = (good_affine_point(pa) +
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good_affine_point(pb) +
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good_jacobian_point(pA) +
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good_jacobian_point(pB) +
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on_weierstrass_curve(A, B, pb) +
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infinite(pA) +
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finite(pB))
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require = finite(pC, lambda pc: constraints(zero={pc.x - pb.x : 'c.x=b.x', pc.y - pb.y : 'c.y=b.y'}))
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return (assumeLaw, require)
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def law_jacobian_weierstrass_add_infinite_b(A, B, pa, pb, pA, pB, pC):
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assumeLaw = (good_affine_point(pa) +
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good_affine_point(pb) +
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good_jacobian_point(pA) +
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good_jacobian_point(pB) +
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on_weierstrass_curve(A, B, pa) +
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infinite(pB) +
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finite(pA))
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require = finite(pC, lambda pc: constraints(zero={pc.x - pa.x : 'c.x=a.x', pc.y - pa.y : 'c.y=a.y'}))
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return (assumeLaw, require)
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def law_jacobian_weierstrass_add_infinite_ab(A, B, pa, pb, pA, pB, pC):
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assumeLaw = (good_affine_point(pa) +
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good_affine_point(pb) +
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good_jacobian_point(pA) +
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good_jacobian_point(pB) +
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infinite(pA) +
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infinite(pB))
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require = infinite(pC)
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return (assumeLaw, require)
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laws_jacobian_weierstrass = {
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'add': law_jacobian_weierstrass_add,
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'double': law_jacobian_weierstrass_double,
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'add_opposite': law_jacobian_weierstrass_add_opposites,
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'add_infinite_a': law_jacobian_weierstrass_add_infinite_a,
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'add_infinite_b': law_jacobian_weierstrass_add_infinite_b,
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'add_infinite_ab': law_jacobian_weierstrass_add_infinite_ab
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}
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def check_exhaustive_jacobian_weierstrass(name, A, B, branches, formula, p):
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"""Verify an implementation of addition of Jacobian points on a Weierstrass curve, by executing and validating the result for every possible addition in a prime field"""
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F = Integers(p)
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print("Formula %s on Z%i:" % (name, p))
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points = []
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for x in range(0, p):
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for y in range(0, p):
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point = affinepoint(F(x), F(y))
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r, e = concrete_verify(on_weierstrass_curve(A, B, point))
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if r:
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points.append(point)
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ret = True
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for za in range(1, p):
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for zb in range(1, p):
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for pa in points:
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for pb in points:
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for ia in range(2):
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for ib in range(2):
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pA = jacobianpoint(pa.x * F(za)^2, pa.y * F(za)^3, F(za), ia)
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pB = jacobianpoint(pb.x * F(zb)^2, pb.y * F(zb)^3, F(zb), ib)
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for branch in range(0, branches):
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assumeAssert, assumeBranch, pC = formula(branch, pA, pB)
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pC.X = F(pC.X)
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pC.Y = F(pC.Y)
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pC.Z = F(pC.Z)
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pC.Infinity = F(pC.Infinity)
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r, e = concrete_verify(assumeAssert + assumeBranch)
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if r:
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match = False
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for key in laws_jacobian_weierstrass:
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assumeLaw, require = laws_jacobian_weierstrass[key](A, B, pa, pb, pA, pB, pC)
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r, e = concrete_verify(assumeLaw)
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if r:
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if match:
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print(" multiple branches for (%s,%s,%s,%s) + (%s,%s,%s,%s)" % (pA.X, pA.Y, pA.Z, pA.Infinity, pB.X, pB.Y, pB.Z, pB.Infinity))
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else:
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match = True
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r, e = concrete_verify(require)
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if not r:
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ret = False
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print(" failure in branch %i for (%s,%s,%s,%s) + (%s,%s,%s,%s) = (%s,%s,%s,%s): %s" % (branch, pA.X, pA.Y, pA.Z, pA.Infinity, pB.X, pB.Y, pB.Z, pB.Infinity, pC.X, pC.Y, pC.Z, pC.Infinity, e))
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print()
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return ret
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def check_symbolic_function(R, assumeAssert, assumeBranch, f, A, B, pa, pb, pA, pB, pC):
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assumeLaw, require = f(A, B, pa, pb, pA, pB, pC)
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return check_symbolic(R, assumeLaw, assumeAssert, assumeBranch, require)
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def check_symbolic_jacobian_weierstrass(name, A, B, branches, formula):
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"""Verify an implementation of addition of Jacobian points on a Weierstrass curve symbolically"""
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R.<ax,bx,ay,by,Az,Bz,Ai,Bi> = PolynomialRing(QQ,8,order='invlex')
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lift = lambda x: fastfrac(R,x)
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ax = lift(ax)
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ay = lift(ay)
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Az = lift(Az)
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bx = lift(bx)
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by = lift(by)
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Bz = lift(Bz)
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Ai = lift(Ai)
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Bi = lift(Bi)
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pa = affinepoint(ax, ay, Ai)
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pb = affinepoint(bx, by, Bi)
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pA = jacobianpoint(ax * Az^2, ay * Az^3, Az, Ai)
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pB = jacobianpoint(bx * Bz^2, by * Bz^3, Bz, Bi)
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res = {}
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for key in laws_jacobian_weierstrass:
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res[key] = []
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print("Formula " + name + ":")
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count = 0
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ret = True
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for branch in range(branches):
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assumeFormula, assumeBranch, pC = formula(branch, pA, pB)
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assumeBranch = assumeBranch.map(lift)
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assumeFormula = assumeFormula.map(lift)
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pC.X = lift(pC.X)
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pC.Y = lift(pC.Y)
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pC.Z = lift(pC.Z)
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pC.Infinity = lift(pC.Infinity)
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for key in laws_jacobian_weierstrass:
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success, msg = check_symbolic_function(R, assumeFormula, assumeBranch, laws_jacobian_weierstrass[key], A, B, pa, pb, pA, pB, pC)
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if not success:
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ret = False
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res[key].append((msg, branch))
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for key in res:
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print(" %s:" % key)
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val = res[key]
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for x in val:
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if x[0] is not None:
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print(" branch %i: %s" % (x[1], x[0]))
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print()
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return ret
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