Fix Edwards yz/yzsquared to_model.

Fixes #10.

2 files changed, 11 insertions, 3 deletions

diff --git a/pyecsca/ec/curve.py b/pyecsca/ec/curve.py
index 7351583..e976289 100644
--- a/pyecsca/ec/curve.py
+++ b/pyecsca/ec/curve.py
@@ -167,7 +167,10 @@ class EllipticCurve(object):
             return False
         if self.is_neutral(point):
             return True
-        loc = {**self.parameters, **point.to_affine().coords}
+        if isinstance(point.coordinate_model, AffineCoordinateModel):
+            loc = {**self.parameters, **point.coords}
+        else:
+            loc = {**self.parameters, **point.to_affine().coords}
         return eval(compile(self.model.equation, "", mode="eval"), loc)
 
     def to_affine(self) -> "EllipticCurve":
diff --git a/pyecsca/ec/point.py b/pyecsca/ec/point.py
index 480c47f..a3c388e 100644
--- a/pyecsca/ec/point.py
+++ b/pyecsca/ec/point.py
@@ -103,8 +103,13 @@ class Point(object):
                         result[var] = result[var].inverse()
                 elif var == "Y":
                     result[var] = self.coords["y"]
-                    if isinstance(coordinate_model, EFDCoordinateModel) and coordinate_model.name == "inverted":
-                        result[var] = result[var].inverse()
+                    if isinstance(coordinate_model, EFDCoordinateModel):
+                        if coordinate_model.name == "inverted":
+                            result[var] = result[var].inverse()
+                        elif coordinate_model.name == "yz":
+                            result[var] = result[var] * curve.parameters["r"]
+                        elif coordinate_model.name == "yzsquared":
+                            result[var] = result[var] * curve.parameters["r"]**2
                 elif var.startswith("Z"):
                     result[var] = Mod(1, curve.prime)
                 elif var == "T":