RE: [WM]: Cox book

["Matthew Miller" <mlm@research.nj.nec.com>]

Khalid,

I apologize for the confusion.  Here's the reason for the difference:

On page 98, we're talking about the minimum possible inner product
between two messages that differ in h symbols.  This minimum is taken
over all possible sets of reference marks, W_AL.

On page 99, we're assuming that W_AL is designed to yield this lowest
possible inner product, and talking about the closest pair of code words
in our code.  If this pair differs in h symbols, then their minimum
inner product is N(L-2h), and we assume that this is the inner product
W_AL gives.  The maximum we're discussing is taken over all possible
pairs of code words -- the closest two (the two that differ in the
fewest bits) yield the maximum inner product.

It's a subtle distinction, and rereading it now I agree it's not
terribly clear.  We should probably have made the assumption about W_AL
explicit, and maybe devoted a footnote to explaining why
N(L-2h) is a minimum on one page and a maximum on the next.  I hope my
above explanation helps.

Thanks for pointing this out.

-- Matt



-----Original Message-----
From: watermarking-owner@watermarkingworld.org
[mailto:watermarking-owner@watermarkingworld.org]On Behalf Of khalid
mahmoud
Sent: Tuesday, August 20, 2002 3:17 PM
To: watermarking@watermarkingworld.org
Subject: [WM]: Cox book


hi all,
i am now read the Cox book, and i reach ch4
on page 98: he say that n(l-2h) is the smallest inner
product
while in the next page say that is a maximum?!!!!
can any body clarify this for me
thanks
khalid


=====
Khalid Waleed Mahmoud
ZPU University
P.O.Box 2000
Zarka - 13110
Jordan



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