lightweight encryption of text file

Robert Kern robert.kern at
Fri Jan 8 20:51:47 CET 2010

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
> 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 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.

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

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