| # -*- 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. |
| ''' |
| |
| |
| from rsa._compat import is_integer |
| |
| def assert_int(var, name): |
| |
| if is_integer(var): |
| 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''' |
| |
| assert_int(cyphertext, 'cyphertext') |
| assert_int(dkey, 'dkey') |
| assert_int(n, 'n') |
| |
| message = pow(cyphertext, dkey, n) |
| return message |
| |