Substitution Cipher

gistfile1.py

#!/usr/bin/env python
from string import printable, maketrans
from random import seed, shuffle

def cipher_alphabet(key):
  alphabet = [c for c in printable]
  seed(hash(key))
  shuffle(alphabet)
  return ''.join(alphabet)

def encrypt(key, message):
  return message.translate(maketrans(printable, cipher_alphabet(key)))

def decrypt(key, message):
  return message.translate(maketrans(cipher_alphabet(key), printable))

# Sample usage:
key = 'password'
message = 'This is a message'
print encrypt(key, message)
print decrypt(key, encrypt(key, message))