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1998-05-11 - Re: Chaffing & winnowing without overhead

Header Data

From: “Mordechai Ovits” <movits@syndata.com>
To: “Jes�s Cea Avi�n” <jcea@argo.es>
Message Hash: ec8de4f9d6a290fe574f95e0716aebbe2618b7f3105c77acf95a847e4a713a89
Message ID: <35574C41.816CA545@syndata.com>
Reply To: <35571323.D109A0D2@argo.es>
UTC Datetime: 1998-05-11 19:10:06 UTC
Raw Date: Mon, 11 May 1998 12:10:06 -0700 (PDT)

Raw message

From: "Mordechai Ovits" <movits@syndata.com>
Date: Mon, 11 May 1998 12:10:06 -0700 (PDT)
To: "Jess Cea Avin" <jcea@argo.es>
Subject: Re: Chaffing & winnowing without overhead
In-Reply-To: <35571323.D109A0D2@argo.es>
Message-ID: <35574C41.816CA545@syndata.com>
MIME-Version: 1.0
Content-Type: text/plain


Jess Cea Avin wrote:

> In the Rivest's paper you transmit, indeed, all the 2^n plaintexts for a
> n bit length };-).

Not so. In his paper (before the package tranform stuff), he had the following expansion.
Assuming a 32 bit serial number and a 160 bit MAC, n bits would expand to 388n.
This is because Ron is sending it out like this:
quote from http://theory.lcs.mit.edu/~rivest/chaffing.txt
>To make this clearer with an example, note that the adversary 
>will see triples of the form:
>        (1,0,351216)
>        (1,1,895634)
>        (2,0,452412)
>        (2,1,534981)
>        (3,0,639723)
>        (3,1,905344)
>        (4,0,321329)
>        (4,1,978823)
>        ...
>and so on.

Every bit is getting 2 32-bit serial numbers, its own complement, and 2 160-bit MACs.
a 10KB file would explode into a 3.789MB file.
Not too practical, eh? :-)
-- 
o Mordy Ovits
o Programmer / Cryptographer
o SynData Technologies Inc.
o Download A Free Copy Of Our Software At:
o http://www.syncrypt.com

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