1 files changed, 118 insertions, 0 deletions
diff --git a/lib/Crypto/Math/_IntegerCustom.py b/lib/Crypto/Math/_IntegerCustom.py
new file mode 100644
index 0000000..d6f6f75
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+++ b/lib/Crypto/Math/_IntegerCustom.py
@@ -0,0 +1,118 @@
+# ===================================================================
+#
+# Copyright (c) 2018, Helder Eijs <helderijs@gmail.com>
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+# ===================================================================
+
+from ._IntegerNative import IntegerNative
+
+from Crypto.Util.number import long_to_bytes, bytes_to_long
+
+from Crypto.Util._raw_api import (load_pycryptodome_raw_lib,
+                                  create_string_buffer,
+                                  get_raw_buffer, backend,
+                                  c_size_t, c_ulonglong)
+
+
+from Crypto.Random.random import getrandbits
+
+c_defs = """
+int monty_pow(const uint8_t *base,
+               const uint8_t *exp,
+               const uint8_t *modulus,
+               uint8_t       *out,
+               size_t len,
+               uint64_t seed);
+"""
+
+
+_raw_montgomery = load_pycryptodome_raw_lib("Crypto.Math._modexp", c_defs)
+implementation = {"library": "custom", "api": backend}
+
+
+class IntegerCustom(IntegerNative):
+
+    @staticmethod
+    def from_bytes(byte_string, byteorder='big'):
+        if byteorder == 'big':
+            pass
+        elif byteorder == 'little':
+            byte_string = bytearray(byte_string)
+            byte_string.reverse()
+        else:
+            raise ValueError("Incorrect byteorder")
+        return IntegerCustom(bytes_to_long(byte_string))
+
+    def inplace_pow(self, exponent, modulus=None):
+        exp_value = int(exponent)
+        if exp_value < 0:
+            raise ValueError("Exponent must not be negative")
+
+        # No modular reduction
+        if modulus is None:
+            self._value = pow(self._value, exp_value)
+            return self
+
+        # With modular reduction
+        mod_value = int(modulus)
+        if mod_value < 0:
+            raise ValueError("Modulus must be positive")
+        if mod_value == 0:
+            raise ZeroDivisionError("Modulus cannot be zero")
+
+        # C extension only works with odd moduli
+        if (mod_value & 1) == 0:
+            self._value = pow(self._value, exp_value, mod_value)
+            return self
+
+        # C extension only works with bases smaller than modulus
+        if self._value >= mod_value:
+            self._value %= mod_value
+
+        max_len = len(long_to_bytes(max(self._value, exp_value, mod_value)))
+
+        base_b = long_to_bytes(self._value, max_len)
+        exp_b = long_to_bytes(exp_value, max_len)
+        modulus_b = long_to_bytes(mod_value, max_len)
+
+        out = create_string_buffer(max_len)
+
+        error = _raw_montgomery.monty_pow(
+                    out,
+                    base_b,
+                    exp_b,
+                    modulus_b,
+                    c_size_t(max_len),
+                    c_ulonglong(getrandbits(64))
+                    )
+
+        if error:
+            raise ValueError("monty_pow failed with error: %d" % error)
+
+        result = bytes_to_long(get_raw_buffer(out))
+        self._value = result
+        return self