dencode.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import argparse
import base64
import getpass
import math
import sys

def padpad(pad, text):
    if len(text) > len(pad):
        factor = int(math.ceil(float(len(text)) / len(pad)))
        pad = (pad * factor)[:len(text)]
    return pad


def _xor(text, pad):
    return ''.join(chr(ord(a) ^ ord(b)) for a, b in zip(text, pad))

def encode(plaintext, pad):
    pad = padpad(pad, plaintext)
    ciphertext = _xor(plaintext, pad)
    return base64.encodestring(ciphertext)

def decode(ciphertext, pad):
    pad = padpad(pad, ciphertext)
    ciphertext = base64.decodestring(ciphertext)
    plaintext = _xor(ciphertext, pad)
    return plaintext


def main():
    argparser = argparse.ArgumentParser()
    argparser.add_argument('action', choices=['encode', 'decode'])
    args = argparser.parse_args()

    encoding = args.action == 'encode'

    text = (raw_input if not encoding else getpass.getpass)('Enter ' + ('plaintext' if encoding else 'ciphertext') + ': ')
    pad = getpass.getpass('Enter password: ')

    print (encode if encoding else decode)(text, pad)


if __name__ == '__main__':
    main()