2 files changed, 17 insertions, 2 deletions

diff --git a/pyecsca/sca/re/rpa.py b/pyecsca/sca/re/rpa.py
index f21429a..4330fb4 100644
--- a/pyecsca/sca/re/rpa.py
+++ b/pyecsca/sca/re/rpa.py
@@ -36,8 +36,15 @@ class MultipleContext(Context):
 
     def enter_action(self, action: Action) -> None:
         if isinstance(action, (ScalarMultiplicationAction, PrecomputationAction)):
-            self.base = action.point
-            self.points = {self.base: 1}
+            if self.base:
+                # If we already did some computation with this context try to see if we are building on top of it.
+                if self.base != action.point:
+                    # If we are not building on top of it we have to forget stuff and set a new base and mapping.
+                    self.base = action.point
+                    self.points = {self.base: 1}
+            else:
+                self.base = action.point
+                self.points = {self.base: 1}
             self.inside = True
 
     def exit_action(self, action: Action) -> None:
diff --git a/test/sca/test_rpa.py b/test/sca/test_rpa.py
index ac8392e..b33915e 100644
--- a/test/sca/test_rpa.py
+++ b/test/sca/test_rpa.py
@@ -26,6 +26,7 @@ class MultipleContextTests(TestCase):
 
     @parameterized.expand(
         [
+            ("5", 5),
             ("10", 10),
             ("2355498743", 2355498743),
             (
@@ -63,6 +64,13 @@ class MultipleContextTests(TestCase):
         muls = list(ctx.points.values())
         self.assertListEqual(muls, [1, 2, 3, 5])
 
+    def test_window(self):
+        mult = WindowNAFMultiplier(self.add, self.dbl, self.neg, 3, precompute_negation=True)
+        with local(MultipleContext()) as ctx:
+            mult.init(self.secp128r1, self.base)
+            mult.multiply(5)
+        print(ctx.points.values())
+
     def test_ladder(self):
         curve25519 = get_params("other", "Curve25519", "xz")
         base = curve25519.generator