PyCrypto Example using Python 3

gistfile1.txt

{
 "metadata": {
  "name": "PyCrypto_Example"
 },
 "nbformat": 3,
 "nbformat_minor": 0,
 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "# This code taken from youtube example: https://www.youtube.com/watch?v=8PzDfykGg_g&feature=youtube_gdata_player\n# but modified to work with Python 3 due to byte string to string conversion using decode('utf-8') method\n\nfrom Crypto.Cipher import AES  # Dependency: install pycrypto - available at pypi: pip install pycrypto\nimport base64\nimport os\nimport codecs # This is needed to convert a string with single backslashes to byte string\n\ndef encryption(privateInfo):\n    \"\"\" Method to encrypt your message using AES encryption\"\"\"\n    \n    BLOCK_SIZE = 16\n    PADDING = '{'\n\n    pad = lambda s: s + (BLOCK_SIZE - len(s) % BLOCK_SIZE) * PADDING\n\n    EncodeAES = lambda c, s: base64.b64encode(c.encrypt(pad(s)))\n\n    secret = os.urandom(BLOCK_SIZE)  # Comment this line and uncomment line below to use hard-coded key\n    #secret = b'\\xf9J\\xa4\\xd1\\t\\x17\\xb8\\xabt\\xfe\\x06\\x96\\xe3\\xe8(.'\n    print('Encryption key:', secret)\n\n    cipher = AES.new(secret)\n\n    encoded = EncodeAES(cipher, privateInfo)\n    print('Encrypted string:', encoded.decode('UTF-8'))\n\n\ndef decrypt_key_hardcoded(encryptedString):\n    \"\"\" Method to decrypt message using a hard-coded decryption key \"\"\"\n    \n    PADDING = '{'\n    DecodeAES = lambda c, e: c.decrypt(base64.b64decode(e)).decode('utf-8').rstrip(PADDING)\n    #DecodeAES = lambda c, e: c.decrypt(base64.b64decode(e)).rstrip(PADDING)\n    key = b'\\xf9J\\xa4\\xd1\\t\\x17\\xb8\\xabt\\xfe\\x06\\x96\\xe3\\xe8(.'\n    try:\n        cipher = AES.new(key)\n        decoded = DecodeAES(cipher, encryptedString)\n        print('Decoded:', decoded)\n    except:\n        print(\"Error in decoding the secret message\")\n        \ndef decrypt_with_key(key, encryptedString):\n    \"\"\" Method to decrypt message using a decryptionn key passed in as a parameter \"\"\"\n    \n    PADDING = '{'\n    DecodeAES = lambda c, e: c.decrypt(base64.b64decode(e)).decode('utf-8').rstrip(PADDING)\n    try:\n        cipher = AES.new(key)\n        decoded = DecodeAES(cipher, encryptedString)\n        print('Decoded:', decoded)\n    except:\n        print(\"Error in decoding the secret message\")",
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 11
    },
    {
     "cell_type": "heading",
     "level": 4,
     "metadata": {},
     "source": "Let's encrypt our secret message"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "secret_message = input(\"Enter your secret message: \")\nencryption(secret_message)",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "name": "stdout",
       "output_type": "stream",
       "stream": "stdout",
       "text": "Enter your secret message: Message I don't want the government to see\n"
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "Encryption key: b'\\x06\\n\\xf5\\xd2\\x99\\xd0t\\x9fv\\x1b\\xcf\\xfe8\\xab\\x1e-'\nEncrypted string: ZQRLOzBcrXpLkCvk1Ofjr7ALZdJMcrDalXvwGDu4Bwx7ck/FXdo8WIFibE1r37Vn\n"
      }
     ],
     "prompt_number": 12
    },
    {
     "cell_type": "heading",
     "level": 4,
     "metadata": {},
     "source": "Let's decrypt the message by passing in the decryption key"
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": "encoded_string = input(\"Copy/paste the encrypted string here: \")\nkey = input(\"Copy/paste the decryption key here (without the b and single quotes): \")\ndecrypt_with_key(codecs.escape_decode(key)[0], encoded_string)",
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "name": "stdout",
       "output_type": "stream",
       "stream": "stdout",
       "text": "Copy/paste the encrypted string here: ZQRLOzBcrXpLkCvk1Ofjr7ALZdJMcrDalXvwGDu4Bwx7ck/FXdo8WIFibE1r37Vn\n"
      },
      {
       "name": "stdout",
       "output_type": "stream",
       "stream": "stdout",
       "text": "Copy/paste the decryption key here (without the b and single quotes): \\x06\\n\\xf5\\xd2\\x99\\xd0t\\x9fv\\x1b\\xcf\\xfe8\\xab\\x1e-\n"
      },
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": "Decoded: Message I don't want the government to see\n"
      }
     ],
     "prompt_number": 14
    }
   ],
   "metadata": {}
  }
 ]
}