71 lines
2.6 KiB
Python
71 lines
2.6 KiB
Python
# -*- coding: utf-8 -*-
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# Author: Sammy Pfeiffer
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# Author: Anton Grigoryev
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# This file implements the AES 256 IGE cipher
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# working in Python 2.7 and Python 3.4 (other versions untested)
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# as it's needed for the implementation of Telegram API
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# It's based on PyCryto
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from __future__ import print_function
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from Crypto.Util.strxor import strxor
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from Crypto.Cipher import AES
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class IGE:
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def __init__(self, key, iv):
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if len(key) != 32:
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raise ValueError("key must be 32 bytes long (was " +
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str(len(key)) + " bytes)")
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if len(iv) != 32:
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raise ValueError("iv must be 32 bytes long (was " +
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str(len(iv)) + " bytes)")
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self.key = key
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self.iv = iv
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self.cipher = AES.new(key, AES.MODE_ECB, iv)
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def encrypt(self, message):
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return self._ige(message, operation="encrypt")
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def decrypt(self, message):
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return self._ige(message, operation="decrypt")
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def _ige(self, message, operation="decrypt"):
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"""Given a key, given an iv, and message
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do whatever operation asked in the operation field.
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Operation will be checked for: "decrypt" and "encrypt" strings.
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Returns the message encrypted/decrypted.
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message must be a multiple by 16 bytes (for division in 16 byte blocks)
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key must be 32 byte
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iv must be 32 byte (it's not internally used in AES 256 ECB, but it's
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needed for IGE)"""
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blocksize = self.cipher.block_size
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if len(message) % blocksize != 0:
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raise ValueError("message must be a multiple of 16 bytes (try adding " +
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str(16 - len(message) % 16) + " bytes of padding)")
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ivp = self.iv[0:blocksize]
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ivp2 = self.iv[blocksize:]
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ciphered = bytearray()
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for i in range(0, len(message), blocksize):
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indata = message[i:i+blocksize]
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if operation == "decrypt":
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xored = strxor(indata, ivp2)
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decrypt_xored = self.cipher.decrypt(xored)
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outdata = strxor(decrypt_xored, ivp)
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ivp = indata
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ivp2 = outdata
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elif operation == "encrypt":
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xored = strxor(indata, ivp)
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encrypt_xored = self.cipher.encrypt(xored)
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outdata = strxor(encrypt_xored, ivp2)
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ivp = outdata
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ivp2 = indata
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else:
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raise ValueError("operation must be either 'decrypt' or 'encrypt'")
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ciphered.extend(outdata)
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return ciphered |