tests for x=0 and y=0 for points on curve

Author: tomato42

src/ecdsa/ellipticcurve.py

@@ -803,7 +803,7 @@ def double(self):
 
         X3, Y3, Z3 = self._double(X1, Y1, Z1, p, a)
 
-        if not Y3 and not X3:
+        if (not X3 and not Y3) or not Z3:
             return INFINITY
         return PointJacobi(self.__curve, X3, Y3, Z3, self.__order)
 
@@ -941,7 +941,7 @@ def _mul_precompute(self, other):
             else:
                 other //= 2
 
-        if not Y3 or not Z3:
+        if (not X3 and not Y3) or not Z3:
             return INFINITY
         return PointJacobi(self.__curve, X3, Y3, Z3, self.__order)
 

src/ecdsa/test_jacobi.py

@@ -195,6 +195,33 @@ def test_compare_non_zero_with_infinity(self):
 
         self.assertNotEqual(pj, INFINITY)
 
+    def test_compare_non_zero_bad_scale_with_infinity(self):
+        pj = PointJacobi(curve_256, 1, 1, 0)
+        self.assertEqual(pj, INFINITY)
+
+    def test_eq_x_0_on_curve_with_infinity(self):
+        c_23 = CurveFp(23, 1, 1)
+        pj = PointJacobi(c_23, 0, 1, 1)
+
+        self.assertTrue(c_23.contains_point(0, 1))
+
+        self.assertNotEqual(pj, INFINITY)
+
+    def test_eq_y_0_on_curve_with_infinity(self):
+        c_23 = CurveFp(23, 1, 1)
+        pj = PointJacobi(c_23, 4, 0, 1)
+
+        self.assertTrue(c_23.contains_point(4, 0))
+
+        self.assertNotEqual(pj, INFINITY)
+
+    def test_eq_with_same_x_different_y(self):
+        c_23 = CurveFp(23, 1, 1)
+        p_a = PointJacobi(c_23, 0, 22, 1)
+        p_b = PointJacobi(c_23, 0, 1, 1)
+
+        self.assertNotEqual(p_a, p_b)
+
     def test_compare_zero_point_with_infinity(self):
         pj = PointJacobi(curve_256, 0, 0, 1)
 
@@ -671,6 +698,41 @@ def test_add_to_infinity(self):
         self.assertEqual(p3, INFINITY)
         self.assertIs(p3, INFINITY)
 
+    def test_mul_to_x_0(self):
+        c_23 = CurveFp(23, 1, 1)
+        p = PointJacobi(c_23, 9, 7, 1)
+
+        p2 = p * 13
+        self.assertEqual((p2.x(), p2.y()), (0, 22))
+
+    def test_mul_to_y_0(self):
+        c_23 = CurveFp(23, 1, 1)
+        p = PointJacobi(c_23, 9, 7, 1)
+
+        p2 = p * 14
+        self.assertEqual((p2.x(), p2.y()), (4, 0))
+
+    def test_add_to_x_0(self):
+        c_23 = CurveFp(23, 1, 1)
+        p = PointJacobi(c_23, 9, 7, 1)
+
+        p2 = p * 12 + p
+        self.assertEqual((p2.x(), p2.y()), (0, 22))
+
+    def test_add_to_y_0(self):
+        c_23 = CurveFp(23, 1, 1)
+        p = PointJacobi(c_23, 9, 7, 1)
+
+        p2 = p * 13 + p
+        self.assertEqual((p2.x(), p2.y()), (4, 0))
+
+    def test_add_diff_z_to_infinity(self):
+        c_23 = CurveFp(23, 1, 1)
+        p = PointJacobi(c_23, 9, 7, 1)
+
+        c = p * 20 + p * 8
+        self.assertIs(c, INFINITY)
+
     def test_pickle(self):
         pj = PointJacobi(curve=CurveFp(23, 1, 1, 1), x=2, y=3, z=1, order=1)
         self.assertEqual(pickle.loads(pickle.dumps(pj)), pj)