An idle thought on CBC and block lengths

[The Deviant]

On Wed, 25 Sep 1996 PhneCards at aol.com wrote:

> Date: Wed, 25 Sep 1996 18:12:14 -0400
> From: PhneCards at aol.com
> To: osborne at gateway.grumman.com, cypherpunks at toad.com
> Subject: Re: An idle thought on CBC and block lengths
> 
> Did you know this company is using your email address as part of
> an unlawful email bomb?
> 
> I would advise you to write to them at cypherpunks at toad.com
> and owner-cypherpunks at toad.com and advise them to stop
> using your email address for this type of activity.
> 
> It is illegal to use a invalid return email address.  If this continues, I
> will
> be forced to prosecute the return email address - which they are
> making to look like you.

Is it?  I beleive that if you look closely, you will discover hat all the
laws which would have made lying illegal on the 'Net have now been
repealed by more Federal judges than I can count on 1 hand...

> 
> Below is the letter that I received in my email box
> =================================================
> 
> In a message dated 96-09-25 15:52:17 EDT, you write:
> 
> >Subj:	An idle thought on CBC and block lengths
> >Date:	96-09-25 15:52:17 EDT
> >From:	osborne at gateway.grumman.com (Rick Osborne)
> >Sender:	owner-cypherpunks at toad.com
> >To:	cypherpunks at toad.com
> >
> >So I was sitting bored at home and thinking to myself: CBC is cool.
> >Without the key, you're screwed because a single bit error propagates
> >throughout the entire message.  But then I was thinking, yeah, but you can
> >still eventually get the ONE key.  So I began to wonder what the difference
> >in security is between encrypting an entire M with just one K in CBC, or
> >encrypting M with permutations of K over specific block lengths.
> >
> >On the one hand you've got just one key, which makes it that much harder to
> >find in the keyspace.  On the other hand, If evil interloper Eve gets her
> >hands it, she has to find all of the keys to get all of M.  (Assuming she
> >is using brute force and can't necessarily find the master K to permute
> >into the subkeys.)
> >
> >The downsides are of course that on the one side you've got just one key,
> >and once you get it, you get M.  But on the other hand, you can get any one
> >part of the message with less difficulty because of the higher number of
> >keys.  And, of course, if your master K is easy to brute force, then it's
> >actually worse than the first option.
> >
> >Does anyone have opinions / knowledge of which is better?
> >
> >
> >____________________________________________________________
> >Rick Osborne                     osborne at gateway.grumman.com
> >"The universe doesn't give you any points for doing things that are easy."
> >
> >
> >
> >----------------------- Headers --------------------------------
> >From cypherpunks-errors at toad.com  Wed Sep 25 15:51:46 1996
> >Return-Path: cypherpunks-errors at toad.com
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> Wed,
> >25 Sep 1996 05:57:32 -0700 (PDT)
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> >Date: Wed, 25 Sep 1996 08:56:45 -0400
> >To: cypherpunks at toad.com
> >From: Rick Osborne <osborne at gateway.grumman.com>
> >Subject: An idle thought on CBC and block lengths
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> 
> 


 --Deviant
A casual stroll through a lunatic asylum shows that faith does not prove
anything.
		-- Friedrich Nietzsche