[rc5] Question for beginner

Bob Krzaczek rskpci at cis.rit.edu
Tue Oct 28 15:09:45 EST 1997

On Tue, 28 Oct 1997, Dawson wrote:

; >You know, sometimes I wonder... perhaps I should have pressed my point
; >harder back in June about searching the first 256th of the 64 bit keyspace
; >while we were searching the 56 bit keyspace.
; <snip>
; My understanding of what came out of this whole issue was that it would work,
; except for the fact that the two contest used different IVs (initialization
; vectors), so each would chain differently, thus rendering that approach
; unusable.

Actually, it wouldn't have.  The IV is part of the CBC wrapper around a
block cipher; it has nothing to do with the cipher "inside".  In our
example, it wouldn't have affected the set up of RC5's expanded key table
(where the bulk of the computing time is spent) at all. 

Hmm.  The "cipher inside".  I like that.  Kinda like "Intel Inside", but
without the religion. 

RC5: The cipher inside. 


Anyway, the point is moot.  I almost felt guilty, later, after having sent
it out to the rest of the list, consuming our bandwidth.  Fortunately, the
feeling soon passed. ;-)


// bob

// Bob Krzaczek                              <http://www.cis.rit.edu/~rskpci/>
// Center for Imaging Science, RIT                        <rskpci at cis.rit.edu>

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