Vernam XOR Stream Cipher with the Mauborgne Constraint

vernam_decrypt.py

def vernam_decrypt(ciphertext, key):
   return bytearray(
           [ ciphertext[i] ^ key[i]
               for i in xrange(len(ciphertext))
           ])

vernam_demo.py

#!/usr/bin/env python

from os import urandom

def vernam_genkey(length):
    return bytearray(urandom(length))

def vernam_encrypt(plaintext, key):
   return bytearray(
           [ plaintext[i] ^ key[i]
               for i in xrange(len(plaintext))
           ])

def vernam_decrypt(ciphertext, key):
   return bytearray(
           [ ciphertext[i] ^ key[i]
               for i in xrange(len(ciphertext))
           ])

plaintext = bytearray('encrypt me')
key = vernam_genkey(len(plaintext))

print 'Before encrypting: ' + plaintext

ciphertext = vernam_encrypt(plaintext, key)

print 'After encrypting: ' + ciphertext

plaintext2 = vernam_decrypt(ciphertext, key)

print 'After decrypting: ' + plaintext2

vernam_encrypt.py

def vernam_encrypt(plaintext, key):
   return bytearray(
           [ plaintext[i] ^ key[i]
               for i in xrange(len(plaintext))
           ])

vernam_genkey.py

from os import urandom

def vernam_genkey(length):
    return bytearray(urandom(length))