[16642] in cryptography@c2.net mail archive
RE: Cryptography Research wants piracy speed bump on HD DVDs
daemon@ATHENA.MIT.EDU (Bill Frantz)
Wed Jan 5 17:46:53 2005
X-Original-To: cryptography@metzdowd.com
X-Original-To: cryptography@metzdowd.com
Date: Wed, 5 Jan 2005 14:11:11 -0800
From: Bill Frantz <frantz@pwpconsult.com>
To: Marcel Popescu <Marcel_Popescu@microbilt.com>
Cc: cryptography@metzdowd.com
In-Reply-To: <20050105114208.DEBF9F2BF@red.metdow.com>
On 1/5/05, Marcel_Popescu@microbilt.com (Marcel Popescu) wrote:
>Why not the way it happens right now - re-encoding? Few people post DVD
>images of movies on p2p networks, and even when they do, I prefer a DivX o=
r
>XviD variant. (Much better given my 'net bandwidth.) I strongly doubt
>there's any chance of a watermark surviving an unknown re-encoding process
>(DivX has dozens of parameters you can change).
What I have heard from the people building watermark systems is:
(1) The system requirements are that the water mark repeat every few second=
s to mark every part of the work being watermarked. Some systems encrypt t=
he watermark in each repeat block with a different, repeat-block dependent =
key.
(2) By using error correction codes, a short sequences of bits, like a seri=
al number, can be encoded to survive re-encoding. The claim is that you ha=
ve to do serious damage to the quality of the work before the serial number=
becomes unreadable.
Removing the water mark may be quite difficult, but any professional movie =
thief would find the business expense of new players quite affordable. Som=
e individuals might decide that giving a bunch of movies to their friends f=
rom an about-to-be-retired player was a reasonable thing to do. Someone wh=
o works in a store might use an off-the-shelf player. And ... Once a copy=
gets into circulation, it could spread quite widely.
Cheers - Bill
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