X-Git-Url: http://www.git.cypherpunks.ru/?a=blobdiff_plain;f=pygost%2Fgost3410.py;h=58a20e0fe7c6a06020dc90c34e80c76ca78b0150;hb=9ab3b1d03f734f4aae28364f7a6c7c7c223b30a9;hp=b518c95707b48c9d0f3c0741a25a2845c90b2ac0;hpb=82af8726ef5d5e2752089a45750e56c9910398c7;p=pygost.git

diff --git a/pygost/gost3410.py b/pygost/gost3410.py
index b518c95..58a20e0 100644
--- 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
@@ -13,7 +13,7 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
-""" GOST R 34.10 public-key signature function.
+"""GOST R 34.10 public-key signature function.
 
 This is implementation of GOST R 34.10-2001 (:rfc:`5832`), GOST R
 34.10-2012 (:rfc:`7091`). The difference between 2001 and 2012 is the
@@ -35,7 +35,7 @@ def point_size(point):
 
 
 class GOST3410Curve(object):
-    """ GOST 34.10 validated curve
+    """GOST 34.10 validated curve
 
     >>> curve = CURVES["id-GostR3410-2001-TestParamSet"]
     >>> prv = prv_unmarshal(urandom(32))
@@ -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 = (
@@ -219,7 +227,7 @@ DEFAULT_CURVE = CURVES["id-GostR3410-2001-CryptoPro-A-ParamSet"]
 
 
 def public_key(curve, prv):
-    """ Generate public key from the private one
+    """Generate public key from the private one
 
     :param GOST3410Curve curve: curve to use
     :param long prv: private key
@@ -230,7 +238,7 @@ def public_key(curve, prv):
 
 
 def sign(curve, prv, digest, rand=None):
-    """ Calculate signature for provided digest
+    """Calculate signature for provided digest
 
     :param GOST3410Curve curve: curve to use
     :param long prv: private key
@@ -268,7 +276,7 @@ def sign(curve, prv, digest, rand=None):
 
 
 def verify(curve, pub, digest, signature):
-    """ Verify provided digest with the signature
+    """Verify provided digest with the signature
 
     :param GOST3410Curve curve: curve to use
     :type pub: (long, long)
@@ -316,10 +324,26 @@ def prv_unmarshal(prv):
 
     :param bytes prv: serialized private key
     :rtype: long
+
+    It is advisable to use :py:func:`pygost.gost3410.prv_marshal` to
+    assure that key i in curve's Q field for better compatibility with
+    some implementations.
     """
     return bytes2long(prv[::-1])
 
 
+def prv_marshal(curve, prv):
+    """Marshal little-endian private key
+
+    :param GOST3410Curve curve: curve to use
+    :param long prv: serialized private key
+    :rtype: bytes
+
+    Key is in curve's Q field.
+    """
+    return long2bytes(prv % curve.q, point_size(prv))[::-1]
+
+
 def pub_marshal(pub):
     """Marshal public key