DeprecationWarning: decodestring() is a deprecated alias since Python 3.1, use decodebytes()

Hi there,

You might wanna update your script to remove the warning:

```
decrypt.py:76: DeprecationWarning: decodestring() is a deprecated alias since Python 3.1, use decodebytes()
  p = base64.decodestring(bytes(password, 'utf-8'))
```