[5889] in cryptography@c2.net mail archive
Re: "unbreakable code?" with cash prizes
daemon@ATHENA.MIT.EDU (David Honig)
Wed Oct 13 00:10:55 1999
Message-Id: <3.0.5.32.19991012183326.0081b420@pop.sprynet.com>
Date: Tue, 12 Oct 1999 18:33:26 -0700
To: staym@accessdata.com, cryptography@c2.net
From: David Honig <honig@sprynet.com>
In-Reply-To: <3803B85B.2206@accessdata.com>
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At 04:38 PM 10/12/99 -0600, staym@accessdata.com wrote:
>I guess the question is, how much entropy is in your average compressed
>jpeg?
This is by definition empirical. Ie, try it :-)
JPEGs are supposed to be good (nearly full entropy) because the compression
that is typically used is pretty good.
Because JPEG operates under the constraint of 'typical
images being interpretable by humans' it *can't* compress
beyond a certain limit (without becoming some mosaic'd
modern art). Therefore you're unlikely to get the
full bit/baud you need for a decent RNG, unless you
distill & hash further.
My answer: jpeg or any other data, even if compressed, is nonrandom, and
therefore unsuitable for crypto unless
processed further.
