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Re: Whatever happend to compression?
> From: "Perry E. Metzger" <perry@piermont.com>
> Sender: ipsec-approval@neptune.tis.com
> Content-Length: 711
>
>
> Matt Holdrege/Ascend/US writes:
> > A few thoughts.
> >
> > In general, compression is nice in that it randomizes the data first,
> > then encryption further scrambles the bits making it harder for
> > anyone to make sense of it. It's another roadblock to the bad guy.
>
>Any compression scheme you can reverse doesn't randomize the data in
>any meaningful sense. The reason to want compression is to reduce
>bandwidth, not for security.
Actually, I have a paper here in front of me, "Contemporary
Cryptology: An Introduction" by James Massey that talks about
compression and security. The section that talks about this explains
how redundancy in the data can be used to help break "an imperfect
cipher". Since compression removes redundance the article suggests
"...that data compression is a useful cryptographic tool." It goes on
to imply that the practice of removing redundancy from data before
encrypting has been going on for quite some time.
I don't know if this has any relevance to current crypto algorithms
such as DES. I just thought it was interesting that in some instances
compression is/was used to improve security.
Rob G.
rob.glenn@nist.gov
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