"""
P = self.c.p
xx, yy, num, denom, x = ModInt(P), ModInt(P), ModInt(P), ModInt(P), ModInt(P)
yy.mul(y, y)
num.sub(yy, self.c.one)
denom.add(denom.mul(yy, self.c.d), self.c.one)
xx.div(num, denom)
if self.x.jacobi(xx) == 1:
x.sqrt(xx)
newpt = EdwardsPoint(self.c, x, y)
if not newpt._on_curve():
x.sub(P, self.x)
return self.from_ep(newpt)
def decode(self, pt):
"""
Returns the actual data encoded in the point. Checks that the
data is well-formed.
Issues: zero padding doesn't work sometimes?
"""
data = l2b((pt.to_ep(pt).y.v - 1) // k)
return data[1:-2]
Group.register(EdwardsCurve)
Point.register(EdwardsPoint)
Group.__subclasscheck__(EdwardsCurve)
Point.__subclasscheck__(EdwardsPoint)
Group.__instancecheck__(EdwardsCurve)
Point.__instancecheck__(EdwardsPoint)
zero = self.c.zero
negone = self.c.negone
ed = self.c.c.point()
if a._special_pt(a):
if a.equal(self.c.s1):
ed.x.set(zero)
ed.y.set(one)
elif a.equal(self.c.s2):
ed.x.set(zero)
ed.y.set(negone)
elif a.equal(self.c.s4):
ed.x.set(negone)
ed.y.set(zero)
else:
ed.x.set(one)
ed.y.set(zero)
else:
x, y = ModInt(self.c.p), ModInt(self.c.p)
x.div(a.z, a.x)
y.div(a.z, a.y)
ed.x.set(x)
ed.y.set(y)
return ed
Group.register(invEdwardsCurve)
Point.register(invEdwardsPoint)
Group.__subclasscheck__(invEdwardsCurve)
Point.__subclasscheck__(invEdwardsPoint)
Group.__instancecheck__(invEdwardsCurve)
Point.__instancecheck__(invEdwardsPoint)
