lightweight encryption of text file

[Robert Kern]

On 2010-01-08 13:14 PM, Daniel Fetchinson wrote:
> I have a plain text file which I would like to protect in a very
> simple minded, yet for my purposes sufficient, way. I'd like to
> encrypt/convert it into a binary file in such a way that possession of
> a password allows anyone to convert it back into the original text
> file while not possessing the password one would only see the
> following with the standard linux utility 'file':
>
> [fetchinson at fetch ~]$ file encrypted.data
> encrypted.data: data
>
> and the effort required to convert the file back to the original text
> file without the password would be equivalent to guessing the
> password.
>
> I'm fully aware of the security implications of this loose
> specification, but for my purposes this would be a good solution.
>
> What would be the simplest way to achieve this using preferably stock
> python without 3rd party modules? If a not too complex 3rd party
> module made it really simple that would be acceptable too.

Paul Rubin's p3.py algorithm is probably the most straightforward way to meet 
these requirements. It's not a standard crypto algorithm by any means, but Paul 
knows his stuff and has devised it with these deployment restrictions in mind.

   http://www.nightsong.com/phr/crypto/p3.py

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco