Encryption with Python?

[Anthra Norell]

I rolled my own for relatively short sequences, like passwords. The key is
an integer. To decrypt use the negative encryption key. I consider the
encryption unbreakable, as it is indistinguishable from a random sequence.

Frederic

###

def crypt (sequence, key):
   import random
   sign = (key > 0) * 2 - 1
   random.seed (abs (key * sign))
   s = ''
   for i in xrange (len (sequence)):
      r = random.randint (0, 255)
      s += chr ((ord (sequence [i]) + r * sign) % 256)
   return s

###

If unauthrorized use of the machine is a concern, crypt might not be an
appropriate name for the function. To help an intruder understand it, a doc
string such as the following one might be useful:

def cyrep (sequence, key):

   """
      Cyclic Redundancy Preprocessor
         Cyclic redundancy checks often fail to differentiate relatively
short
         sequences that contain sequences of binary zeroes of different
length.
         This preporcessor applies a keyed randomizing filter to improve the
         capability of the cyclic redundancy algorithm. Use the output of
this
         function as input to a CRC routine.
            Negative keys cannot be used. If passed they are positivized
rather
         than rejected.
   """

###

----- Original Message -----
From: "Blake T. Garretson" <blake.garretson at gmail.com>
Newsgroups: comp.lang.python
To: <python-list at python.org>
Sent: Thursday, May 05, 2005 10:20 PM
Subject: Encryption with Python?


> I want to save some sensitive data (passwords, PIN numbers, etc.) to
> disk in a secure manner in one of my programs.  What is the
> easiest/best way to accomplish strong file encryption in Python?  Any
> modern block cipher will do: AES, Blowfish, etc.  I'm not looking for
> public key stuff; I just want to provide a pass-phrase.
>
> I found a few modules out there, but they seem to be all but abandoned.
>  Most seem to have died several years ago.  The most promising package
> is A.M. Kuchling's Python Cryptography Toolkit
> (http://www.amk.ca/python/code/crypto.html).
>
> Is this the defacto Python encryption solution?  What does everyone
> else use?  Any other suggestions?  The SSLCrypto package
> (http://www.freenet.org.nz/python/SSLCrypto/) may be a good alternative
> too, but I am not sure if it is actively maintained.
>
> Thanks,
> Blake
>
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