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Date: Fri, 31 Aug 2012 02:25:18 -0700 (PDT)
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Subject: Re: Question: re Image Files.
From: Ludovic Brenta <ludovic@ludovic-brenta.org>
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Date: 2012-08-31T02:25:18-07:00
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Austin Obyrne wrote on comp.lang.ada:
> That is precisely what I want to do - I have no other interest in
> the image file apart from using the alpha + pixels dat as the
> operands of encryption transformations.

So, you want an attacker of your encryption scheme to know that the
cleartext is an image? And to know the structure of the image file
format?  That doesn't sound like encryption to me.  Proper
encryption should not only obscure the contents but also, and most
importantly, the structure of the cleartext.  All current encryption
methods make an explicit effort to be agnostic about the structure
of whatever it is they encrypt.  For example, disk partitions can
be encrypted at the disk block level -- even directories, file
names and permissions can be encrypted just like everything else,
to give attackers a really hard time extracting any meaningful data
from an encrypted disk.

-- 
Ludovic Brenta.