--- /dev/null
+# -*- coding: utf-8 -*-
+#
+# Copyright 2011 Sybren A. Stüvel <sybren@stuvel.eu>
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+'''Core mathematical operations.
+
+This is the actual core RSA implementation, which is only defined
+mathematically on integers.
+'''
+
+import types
+
+def assert_int(var, name):
+
+ if type(var) in (types.IntType, types.LongType):
+ return
+
+ raise TypeError('%s should be an integer, not %s' % (name, var.__class__))
+
+def encrypt_int(message, ekey, n):
+ """Encrypts a message using encryption key 'ekey', working modulo n"""
+
+ assert_int(message, 'message')
+ assert_int(ekey, 'ekey')
+ assert_int(n, 'n')
+
+ if message < 0:
+ raise ValueError('Only non-negative numbers are supported')
+
+ if message > n:
+ raise OverflowError("The message %i is too long for n=%i" % (message, n))
+
+ return pow(message, ekey, n)
+
+def decrypt_int(cyphertext, dkey, n):
+ """Decrypts a cypher text using the decryption key 'dkey', working
+ modulo n"""
+
+ if type(cyphertext) not in (types.IntType, types.LongType):
+ raise TypeError('cyphertext should be an integer, not %s' %
+ cyphertext.__type__)
+
+ assert_int(cyphertext, 'cyphertext')
+ assert_int(dkey, 'dkey')
+ assert_int(n, 'n')
+
+ message = pow(cyphertext, dkey, n)
+ return message
+