Add 'curve' attribute to EccPoint and EccXPoint classes

Changelog.rst

@@ -9,6 +9,8 @@ Under development
 * GH#814: RSA keys for PSS can be imported.
 * GH#810: fixed negation of Ed25519 points
 * Add support for Curve25519 / X25519
+* Add attribute ``curve`` to EccPoint and EccXPoint classes,
+  with the canonical name of the curve.
 
 3.20.0 (9 January 2024)
 ++++++++++++++++++++++++++

lib/Crypto/PublicKey/_point.py

@@ -131,6 +131,9 @@ class EccPoint(object):
     * Multiplying a point by a scalar: ``R = S*k``
     * In-place multiplication by a scalar: ``T *= k``
 
+    :ivar curve: The **canonical** name of the curve as defined in the `ECC table`_.
+    :vartype curve: string
+
     :ivar x: The affine X-coordinate of the ECC point
     :vartype x: integer
 
@@ -146,7 +149,7 @@ def __init__(self, x, y, curve="p256"):
             self._curve = _curves[curve]
         except KeyError:
             raise ValueError("Unknown curve name %s" % str(curve))
-        self._curve_name = curve
+        self.curve = self._curve.canonical
 
         if self._curve.id == CurveID.CURVE25519:
             raise ValueError("EccPoint cannot be created for Curve25519")
@@ -217,7 +220,7 @@ def __neg__(self):
     def copy(self):
         """Return a copy of this point."""
         x, y = self.xy
-        np = EccPoint(x, y, self._curve_name)
+        np = EccPoint(x, y, self.curve)
         return np
 
     def is_point_at_infinity(self):
@@ -232,9 +235,9 @@ def point_at_infinity(self):
         """Return the *point-at-infinity* for the curve."""
 
         if self._curve.is_edwards:
-            return EccPoint(0, 1, self._curve_name)
+            return EccPoint(0, 1, self.curve)
         else:
-            return EccPoint(0, 0, self._curve_name)
+            return EccPoint(0, 0, self.curve)
 
     @property
     def x(self):
@@ -333,6 +336,9 @@ class EccXPoint(object):
     * Multiplying a point by a scalar: ``R = S*k``
     * In-place multiplication by a scalar: ``T *= k``
 
+    :ivar curve: The **canonical** name of the curve as defined in the `ECC table`_.
+    :vartype curve: string
+
     :ivar x: The affine X-coordinate of the ECC point
     :vartype x: integer
     """
@@ -346,7 +352,7 @@ def __init__(self, x, curve):
             self._curve = _curves[curve]
         except KeyError:
             raise ValueError("Unknown curve name %s" % str(curve))
-        self._curve_name = curve
+        self.curve = self._curve.canonical
 
         if self._curve.id != CurveID.CURVE25519:
             raise ValueError("EccXPoint can only be created for Curve25519")
@@ -404,7 +410,7 @@ def copy(self):
             x = self.x
         except ValueError:
             return self.point_at_infinity()
-        return EccXPoint(x, self._curve_name)
+        return EccXPoint(x, self.curve)
 
     def is_point_at_infinity(self):
         """``True`` if this is the *point-at-infinity*."""
@@ -418,7 +424,7 @@ def is_point_at_infinity(self):
     def point_at_infinity(self):
         """Return the *point-at-infinity* for the curve."""
 
-        return EccXPoint(self._curve.Gx, self._curve_name) * 0
+        return EccXPoint(self._curve.Gx, self.curve) * 0
 
     @property
     def x(self):

lib/Crypto/PublicKey/_point.pyi

@@ -3,6 +3,7 @@ from typing import Union, Optional, Tuple
 from Crypto.Math.Numbers import Integer
 
 class EccPoint(object):
+    curve: str
     def __init__(self,
                  x: Union[int, Integer],
                  y: Union[int, Integer],
@@ -30,6 +31,7 @@ class EccPoint(object):
 
 
 class EccXPoint(object):
+    curve: str
     def __init__(self,
                  x: Union[int, Integer],
                  curve: Optional[str] = ...) -> None: ...

lib/Crypto/SelfTest/PublicKey/test_ECC_Curve25519.py

@@ -69,6 +69,10 @@ def test_init(self):
         EccXPoint(9, "curve25519")
         EccXPoint(2**255 - 19 + 5, "curve25519")
 
+    def test_curve_attribute(self):
+        point = EccXPoint(9, "curve25519")
+        self.assertEqual(point.curve, "Curve25519")
+
     def test_init_fail(self):
         self.assertRaises(ValueError, EccXPoint, 3*(2**255 - 19), "curve25519")
         self.assertRaises(ValueError, EccXPoint, 9, "curve25518")

lib/Crypto/SelfTest/PublicKey/test_ECC_Ed25519.py

@@ -53,9 +53,12 @@ class TestEccPoint_Ed25519(unittest.TestCase):
     G3xy = {"x": 46896733464454938657123544595386787789046198280132665686241321779790909858396,
             "y": 8324843778533443976490377120369201138301417226297555316741202210403726505172}
 
-    pointG = EccPoint(Gxy['x'], Gxy['y'], curve="Ed25519")
-    pointG2 = EccPoint(G2xy['x'], G2xy['y'], curve="Ed25519")
-    pointG3 = EccPoint(G3xy['x'], G3xy['y'], curve="Ed25519")
+    pointG = EccPoint(Gxy['x'], Gxy['y'], curve="ed25519")
+    pointG2 = EccPoint(G2xy['x'], G2xy['y'], curve="ed25519")
+    pointG3 = EccPoint(G3xy['x'], G3xy['y'], curve="ed25519")
+
+    def test_curve_attribute(self):
+        self.assertEqual(self.pointG.curve, "Ed25519")
 
     def test_init_xy(self):
         EccPoint(self.Gxy['x'], self.Gxy['y'], curve="Ed25519")

lib/Crypto/SelfTest/PublicKey/test_ECC_Ed448.py

@@ -53,9 +53,12 @@ class TestEccPoint_Ed448(unittest.TestCase):
     G3xy = {"x": 0x865886b9108af6455bd64316cb6943332241b8b8cda82c7e2ba077a4a3fcfe8daa9cbf7f6271fd6e862b769465da8575728173286ff2f8f,
             "y": 0xe005a8dbd5125cf706cbda7ad43aa6449a4a8d952356c3b9fce43c82ec4e1d58bb3a331bdb6767f0bffa9a68fed02dafb822ac13588ed6fc}
 
-    pointG = EccPoint(Gxy['x'], Gxy['y'], curve="Ed448")
-    pointG2 = EccPoint(G2xy['x'], G2xy['y'], curve="Ed448")
-    pointG3 = EccPoint(G3xy['x'], G3xy['y'], curve="Ed448")
+    pointG = EccPoint(Gxy['x'], Gxy['y'], curve="ed448")
+    pointG2 = EccPoint(G2xy['x'], G2xy['y'], curve="ed448")
+    pointG3 = EccPoint(G3xy['x'], G3xy['y'], curve="ed448")
+
+    def test_curve_attribute(self):
+        self.assertEqual(self.pointG.curve, "Ed448")
 
     def test_init_xy(self):
         EccPoint(self.Gxy['x'], self.Gxy['y'], curve="Ed448")

lib/Crypto/SelfTest/PublicKey/test_ECC_NIST.py

@@ -86,6 +86,9 @@ class TestEccPoint_NIST_P192(unittest.TestCase):
                 0x264424096af2b3597796db48f8dfb41fa9cecc97691a9c79,
                 curve='p192')
 
+    def test_curve_attribute(self):
+        self.assertEqual(self.pointS.curve, "NIST P-192")
+
     def test_set(self):
         pointW = EccPoint(0, 0)
         pointW.set(self.pointS)
@@ -226,6 +229,9 @@ class TestEccPoint_NIST_P224(unittest.TestCase):
                 0xc42a8a4d34984f0b71b5b4091af7dceb33ea729c1a2dc8b434f10c34,
                 curve='p224')
 
+    def test_curve_attribute(self):
+        self.assertEqual(self.pointS.curve, "NIST P-224")
+
     def test_set(self):
         pointW = EccPoint(0, 0)
         pointW.set(self.pointS)
@@ -364,6 +370,9 @@ class TestEccPoint_NIST_P256(unittest.TestCase):
                 0x55a8b00f8da1d44e62f6b3b25316212e39540dc861c89575bb8cf92e35e0986b,
                 0x5421c3209c2d6c704835d82ac4c3dd90f61a8a52598b9e7ab656e9d8c8b24316)
 
+    def test_curve_attribute(self):
+        self.assertEqual(self.pointS.curve, "NIST P-256")
+
     def test_set(self):
         pointW = EccPoint(0, 0)
         pointW.set(self.pointS)
@@ -504,6 +513,9 @@ class TestEccPoint_NIST_P384(unittest.TestCase):
                 0x84009a263fefba7c2c57cffa5db3634d286131afc0fca8d25afa22a7b5dce0d9470da89233cee178592f49b6fecb5092,
                 "p384")
 
+    def test_curve_attribute(self):
+        self.assertEqual(self.pointS.curve, "NIST P-384")
+
     def test_set(self):
         pointW = EccPoint(0, 0, "p384")
         pointW.set(self.pointS)
@@ -635,6 +647,9 @@ class TestEccPoint_NIST_P521(unittest.TestCase):
                 0x000001fdf842769c707c93c630df6d02eff399a06f1b36fb9684f0b373ed064889629abb92b1ae328fdb45534268384943f0e9222afe03259b32274d35d1b9584c65e305,
                 "p521")
 
+    def test_curve_attribute(self):
+        self.assertEqual(self.pointS.curve, "NIST P-521")
+
     def test_set(self):
         pointW = EccPoint(0, 0)
         pointW.set(self.pointS)