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the calculus of encrypting non-textual data (was Re: concrete steps for improving apt downloading security and privacy)

On Tue, Jul 8, 2014 at 5:13 AM, Andrea Zwirner <andrea@linkspirit.org> wrote:
> On 07/07/2014 13:09, Joel Rees wrote:
> Sorry Joel, I almost totally disagree with your vision on privacy and
> security, but I really i don't want to go into the merit of it, because
> I think Lou is representing my vision already; I only have a question:
>> Did you know that encrypting a picture sometimes results in a picture
>> that looks like it has been through a random color-permuting filter?
> Can you proof it?

Memory of coursework in encryption. The professor did some simple
encryption on uncompressed images and showed how the results tended
not to hide the things one would want hidden.

Then he pointed out that the parts of an image with the most
information are the parts that are least likely to compress. And he
pointed out that standard encryption methods tend to be byte-oriented,
for speed.

He did not require us to do any homework on it, so I don't have any
special tools in my notebooks. 30 years ago. Heh. The technology has
changed somewhat since then, but I recently read about some standard
encrypted sound files that were playable, noisy, but recognizable.
Same principle.

> Or maybe, you can tell the list what the attached image - that is
> encrypted with Moritz Muehlenhoff's and Florian Weimer's public keys -
> represent?

You'll note that I never said it could be done on every encrypted
image. I assume that, now the math has been pointed out to you, you
won't mind if I decline the challenge?

> Cheers (and thanks Mr. Moritz and Mr. Florian - who were the only I had
> in my keyring - to accept being the judges of the challenge). :-)

Give them my regards, and I hope they are not disappointed. I've got
other things to do.

>      Andrea Zwirner
> Sent from my Sylpheed

Joel Rees

Be careful where you see conspiracy.
Look first in your own heart.

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