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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 [email protected]
and [email protected] 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
be forced to prosecute the return email address - which they are
making to look like you.

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:	[email protected] (Rick Osborne)
>Sender:	[email protected]
>To:	[email protected]
>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                     [email protected]
>"The universe doesn't give you any points for doing things that are easy."
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>Date: Wed, 25 Sep 1996 08:56:45 -0400
>To: [email protected]
>From: Rick Osborne <[email protected]>
>Subject: An idle thought on CBC and block lengths
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