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[pygost.git] / pygost / gost3410.py

diff --git a/pygost/gost3410.py b/pygost/gost3410.py
index 433c8188f96144dd7457a308d1cf4c274b805376..88cbfbe3493742e003cc6d9149c93739909207db 100644 (file)
--- a/pygost/gost3410.py
+++ b/pygost/gost3410.py
@@ -1,6 +1,6 @@
 # coding: utf-8
 # PyGOST -- Pure Python GOST cryptographic functions library
-# Copyright (C) 2015-2020 Sergey Matveev <stargrave@stargrave.org>
+# Copyright (C) 2015-2021 Sergey Matveev <stargrave@stargrave.org>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -64,9 +64,7 @@ class GOST3410Curve(object):
         self.cofactor = cofactor
         self.e = e
         self.d = d
-        r1 = self.y * self.y % self.p
-        r2 = ((self.x * self.x + self.a) * self.x + self.b) % self.p
-        if r1 != self.pos(r2):
+        if not self.contains((x, y)):
             raise ValueError("Invalid parameters")
         self._st = None
 
@@ -81,6 +79,16 @@ class GOST3410Curve(object):
             return v + self.p
         return v
 
+    def contains(self, point):
+        """Is point on the curve?
+
+        :type point: (long, long)
+        """
+        x, y = point
+        r1 = y * y % self.p
+        r2 = ((x * x + self.a) * x + self.b) % self.p
+        return r1 == self.pos(r2)
+
     def _add(self, p1x, p1y, p2x, p2y):
         if p1x == p2x and p1y == p2y:
             # double
@@ -112,7 +120,7 @@ class GOST3410Curve(object):
         """Compute s/t parameters for twisted Edwards curve points conversion
         """
         if self.e is None or self.d is None:
-            raise ValueError("non twisted Edwards curve")
+            raise ValueError("Non twisted Edwards curve")
         if self._st is not None:
             return self._st
         self._st = (