Re: [Khufu] Pre-Computing the S-Boxes and obtaining aux. keys
From: Nikola Skoric (nick-news_at_net4u.hr)
Date: 10/31/04
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Date: Sun, 31 Oct 2004 17:23:06 +0100
Dana Sun, 31 Oct 2004 13:44:58 +0000 (UTC)
Zeljko Vrba (ime.prezime@oss.unist.hr) kaze...
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: RIPEMD160
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> In article <MPG.1beefb60f460327c989981@localhost>, Nikola Skoric wrote:
> >>
> >> I am ignorant, but, according to HAC, the algorithm is patented.
> > Pardon me for my ignorance <g> but, what would HAC be?
> >
> Handbook of Applied Cryptography. Available online at
> http://www.cacr.math.uwaterloo.ca/hac/
Many thanks.
Now, would you possibly know is there an online version of "Applied
Cryptography: ..., Second Edition" by Bruce Schneier? I got a hint there
*might* be a full description of Khufu...
> > Now, do you know where could I start asking for patent document?
> >
> >> As to the generation of its S-boxes, which you asked, I have
> >> a 'guess':
> >
> > Exactly what I'm trying to circumvent :-)
> >
> I wonder how you didn't come up with any information. Typing "khufu
> algorithm implementation" into google gives
>
> http://tirnanog.ls.fi.upm.es/Servicios/Software/ap_crypt/indice.html
>
> as its first link.. there you can download khufu implementation together
> with the S-box generator..
Ofcourse I found it... I googled the hell out of the Web and if I didn't
found every possible link available through google, I'd be very
dissapointed. It doesn't take a lot of examination of the archive
available for download on that adress to find this comment in the head
of the KHUFU.C file:
"This is a quick hack to implement/test the Khufu encryption method
described in Ralph Merkle's paper. All but the actual Khufu encryption
algorithm in this code are hacks... they are just for illustration."
So, the point is this guy was in the same position as I am. He has the
algorithm, but he did some quick hacks to get around the fact he hasn't
any clue how to generate auxiliary keys and S-Boxes. The algorithm
itself is well explained in the Merkle's paper and to be honest I didn't
even bother to understand the C code in that file except to ensure that
the function initialize() (which builds the aux key material and the
boxes) is just an ugly hack.
Now, I might be missing something obvious... in that case, I BEG you to
point me in the right direction becouse I'm facing a solid brick wall
here...
-- "Stara boljka se leci starim lekom... Dabome vinom, ta nebi valjda mlekom?"
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