Simple AES encrypt/decrypt

encdec.py

"""
Usage:

    cat '1234567890123456' > secret.key
    echo "hello world" | python encdec.py | python encdec.py -d
"""
import sys
import base64
import getopt

from Crypto.Cipher import AES

_keyfile = 'secret.key'
_secret_key = None

def secret_key():
    global _secret_key
    if _secret_key is None:
        _secret_key = open(_keyfile).read().strip()
    return _secret_key

def enc(msg):
    msg = msg.rjust(32)

    cipher = AES.new(secret_key(), AES.MODE_ECB)
    return base64.b64encode(cipher.encrypt(msg))

def dec(msg):
    cipher = AES.new(secret_key(), AES.MODE_ECB)
    return cipher.decrypt(base64.b64decode(msg)).strip()

def main():
    func = enc

    opts, args = getopt.getopt(sys.argv[1:], 'ds:')
    for o, a in opts:
        if o == '-d': func = dec
        elif o == '-s': _keyfile = a

    sys.stdout.write(func(sys.stdin.read()))

if __name__ == '__main__':
    main()