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1996-04-20 - Re: why compression doesn’t perfectly even out entropy

Header Data

From: “Perry E. Metzger” <perry@piermont.com>
To: “Jon Leonard” <jleonard@divcom.umop-ap.com>
Message Hash: 8350990b02e4a1d189ea182c2a35fb26b1aeaa1222cc7a1c56d4a7cc865097db
Message ID: <199604192048.QAA12275@jekyll.piermont.com>
Reply To: <9604191918.AA17670@divcom.umop-ap.com>
UTC Datetime: 1996-04-20 00:29:46 UTC
Raw Date: Sat, 20 Apr 1996 08:29:46 +0800

Raw message

From: "Perry E. Metzger" <perry@piermont.com>
Date: Sat, 20 Apr 1996 08:29:46 +0800
To: "Jon Leonard" <jleonard@divcom.umop-ap.com>
Subject: Re: why compression doesn't perfectly even out entropy
In-Reply-To: <9604191918.AA17670@divcom.umop-ap.com>
Message-ID: <199604192048.QAA12275@jekyll.piermont.com>
MIME-Version: 1.0
Content-Type: text/plain



"Jon Leonard" writes:
> Perry's right: giving up any statistical information is too much.
>  
> A slightly contrived example of why tossing out duplicated bytes is bad:
>  
> Suppose that a military organization is using this almost one-time-pad
> system, and my spies tell my they've fallen into the habit of sending
> "attack" and "defend" as their only 6-byte messages.  This isn't a problem
> with a real one-time pad (except for traffic analysis...), but this lets
> me determine the message 3.8% of the time!

This could actually be used for traffic analysis in many instances;
you could succeed in extracting small amounts of information from the
passing data.

Any amount of leakage can in some instances be too much...

.pm

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