Initial commit

venv/Lib/site-packages/ecdsa/eddsa.py

@@ -0,0 +1,252 @@
+"""Implementation of Edwards Digital Signature Algorithm."""
+
+import hashlib
+from ._sha3 import shake_256
+from . import ellipticcurve
+from ._compat import (
+    remove_whitespace,
+    bit_length,
+    bytes_to_int,
+    int_to_bytes,
+    compat26_str,
+)
+
+# edwards25519, defined in RFC7748
+_p = 2**255 - 19
+_a = -1
+_d = int(
+    remove_whitespace(
+        "370957059346694393431380835087545651895421138798432190163887855330"
+        "85940283555"
+    )
+)
+_h = 8
+
+_Gx = int(
+    remove_whitespace(
+        "151122213495354007725011514095885315114540126930418572060461132"
+        "83949847762202"
+    )
+)
+_Gy = int(
+    remove_whitespace(
+        "463168356949264781694283940034751631413079938662562256157830336"
+        "03165251855960"
+    )
+)
+_r = 2**252 + 0x14DEF9DEA2F79CD65812631A5CF5D3ED
+
+
+def _sha512(data):
+    return hashlib.new("sha512", compat26_str(data)).digest()
+
+
+curve_ed25519 = ellipticcurve.CurveEdTw(_p, _a, _d, _h, _sha512)
+generator_ed25519 = ellipticcurve.PointEdwards(
+    curve_ed25519, _Gx, _Gy, 1, _Gx * _Gy % _p, _r, generator=True
+)
+
+
+# edwards448, defined in RFC7748
+_p = 2**448 - 2**224 - 1
+_a = 1
+_d = -39081 % _p
+_h = 4
+
+_Gx = int(
+    remove_whitespace(
+        "224580040295924300187604334099896036246789641632564134246125461"
+        "686950415467406032909029192869357953282578032075146446173674602635"
+        "247710"
+    )
+)
+_Gy = int(
+    remove_whitespace(
+        "298819210078481492676017930443930673437544040154080242095928241"
+        "372331506189835876003536878655418784733982303233503462500531545062"
+        "832660"
+    )
+)
+_r = 2**446 - 0x8335DC163BB124B65129C96FDE933D8D723A70AADC873D6D54A7BB0D
+
+
+def _shake256(data):
+    return shake_256(data, 114)
+
+
+curve_ed448 = ellipticcurve.CurveEdTw(_p, _a, _d, _h, _shake256)
+generator_ed448 = ellipticcurve.PointEdwards(
+    curve_ed448, _Gx, _Gy, 1, _Gx * _Gy % _p, _r, generator=True
+)
+
+
+class PublicKey(object):
+    """Public key for the Edwards Digital Signature Algorithm."""
+
+    def __init__(self, generator, public_key, public_point=None):
+        self.generator = generator
+        self.curve = generator.curve()
+        self.__encoded = public_key
+        # plus one for the sign bit and round up
+        self.baselen = (bit_length(self.curve.p()) + 1 + 7) // 8
+        if len(public_key) != self.baselen:
+            raise ValueError(
+                "Incorrect size of the public key, expected: {0} bytes".format(
+                    self.baselen
+                )
+            )
+        if public_point:
+            self.__point = public_point
+        else:
+            self.__point = ellipticcurve.PointEdwards.from_bytes(
+                self.curve, public_key
+            )
+
+    def __eq__(self, other):
+        if isinstance(other, PublicKey):
+            return (
+                self.curve == other.curve and self.__encoded == other.__encoded
+            )
+        return NotImplemented
+
+    def __ne__(self, other):
+        return not self == other
+
+    @property
+    def point(self):
+        return self.__point
+
+    @point.setter
+    def point(self, other):
+        if self.__point != other:
+            raise ValueError("Can't change the coordinates of the point")
+        self.__point = other
+
+    def public_point(self):
+        return self.__point
+
+    def public_key(self):
+        return self.__encoded
+
+    def verify(self, data, signature):
+        """Verify a Pure EdDSA signature over data."""
+        data = compat26_str(data)
+        if len(signature) != 2 * self.baselen:
+            raise ValueError(
+                "Invalid signature length, expected: {0} bytes".format(
+                    2 * self.baselen
+                )
+            )
+        R = ellipticcurve.PointEdwards.from_bytes(
+            self.curve, signature[: self.baselen]
+        )
+        S = bytes_to_int(signature[self.baselen :], "little")
+        if S >= self.generator.order():
+            raise ValueError("Invalid signature")
+
+        dom = bytearray()
+        if self.curve == curve_ed448:
+            dom = bytearray(b"SigEd448" + b"\x00\x00")
+
+        k = bytes_to_int(
+            self.curve.hash_func(dom + R.to_bytes() + self.__encoded + data),
+            "little",
+        )
+
+        if self.generator * S != self.__point * k + R:
+            raise ValueError("Invalid signature")
+
+        return True
+
+
+class PrivateKey(object):
+    """Private key for the Edwards Digital Signature Algorithm."""
+
+    def __init__(self, generator, private_key):
+        self.generator = generator
+        self.curve = generator.curve()
+        # plus one for the sign bit and round up
+        self.baselen = (bit_length(self.curve.p()) + 1 + 7) // 8
+        if len(private_key) != self.baselen:
+            raise ValueError(
+                "Incorrect size of private key, expected: {0} bytes".format(
+                    self.baselen
+                )
+            )
+        self.__private_key = bytes(private_key)
+        self.__h = bytearray(self.curve.hash_func(private_key))
+        self.__public_key = None
+
+        a = self.__h[: self.baselen]
+        a = self._key_prune(a)
+        scalar = bytes_to_int(a, "little")
+        self.__s = scalar
+
+    @property
+    def private_key(self):
+        return self.__private_key
+
+    def __eq__(self, other):
+        if isinstance(other, PrivateKey):
+            return (
+                self.curve == other.curve
+                and self.__private_key == other.__private_key
+            )
+        return NotImplemented
+
+    def __ne__(self, other):
+        return not self == other
+
+    def _key_prune(self, key):
+        # make sure the key is not in a small subgroup
+        h = self.curve.cofactor()
+        if h == 4:
+            h_log = 2
+        elif h == 8:
+            h_log = 3
+        else:
+            raise ValueError("Only cofactor 4 and 8 curves supported")
+        key[0] &= ~((1 << h_log) - 1)
+
+        # ensure the highest bit is set but no higher
+        l = bit_length(self.curve.p())
+        if l % 8 == 0:
+            key[-1] = 0
+            key[-2] |= 0x80
+        else:
+            key[-1] = key[-1] & (1 << (l % 8)) - 1 | 1 << (l % 8) - 1
+        return key
+
+    def public_key(self):
+        """Generate the public key based on the included private key"""
+        if self.__public_key:
+            return self.__public_key
+
+        public_point = self.generator * self.__s
+
+        self.__public_key = PublicKey(
+            self.generator, public_point.to_bytes(), public_point
+        )
+
+        return self.__public_key
+
+    def sign(self, data):
+        """Perform a Pure EdDSA signature over data."""
+        data = compat26_str(data)
+        A = self.public_key().public_key()
+
+        prefix = self.__h[self.baselen :]
+
+        dom = bytearray()
+        if self.curve == curve_ed448:
+            dom = bytearray(b"SigEd448" + b"\x00\x00")
+
+        r = bytes_to_int(self.curve.hash_func(dom + prefix + data), "little")
+        R = (self.generator * r).to_bytes()
+
+        k = bytes_to_int(self.curve.hash_func(dom + R + A + data), "little")
+        k %= self.generator.order()
+
+        S = (r + k * self.__s) % self.generator.order()
+
+        return R + int_to_bytes(S, self.baselen, "little")