Vulnerability Development mailing list archives

hacksdmi?


From: Blue Boar <BlueBoar () THIEVCO COM>
Date: Tue, 10 Oct 2000 22:34:09 -0700

Did anyone else download the hacksdmi.org challenges, and take a look
at them?  I did briefly.  The contest is over, and I think they are
announcing something tomorrow.  The terms of their agreement were
more reasonable that I would have thought.  You could have
the materials... and you really only had to agree to terms if
you planned on going after the money.  You could release your
findings, you'd just forfeit any prize.

So, I figure anyone who wanted to play for the money has done so,
and since the thing is over, we won't be interfering with any
contest by discussing.  naturally, I have my own political agenda,
but that part is off-topic.

OK, onto the fun stuff..

For example, for watermark 1, they give 3 files.  samp1a.wav which
is an untouched .wav, samp2a.wav is the same file, but with a watermark.
samp3a.wav is a different sound file, but with the same watermark.

So, take a look at this:
Comparing files samp1a.wav and samp2a.wav
00000004: E0 24
0000004E: A8 A7
00000050: 0E 0F
00000056: A4 A5
00000058: 4A 49
0000006E: 71 70
00000074: 93 94
00000080: EB EC
00000086: 5A 59
0000008E: 40 41
00000094: 28 29
00000098: 94 93
000000AA: 2E 2D
000000B0: 8B 8A
000000B2: BC BD
000000BA: 7B 7A

Starting at 4E, the watermarked file has some bytes either 1 larger or
one smaller than the unmarked file.  I.e. the low-order bit has
been flipped.  Note that it's only on even bytes.

That's a bit of a short sample, but I don't want to dump any huge files
on anyone.

The original challenge was to strip the watermark so that the detector
program (not provided) wouldn't be able to spot the watermark, and that
some minimum sound quality be maintained.

Anyone else fiddled with this?  Later, I'll write some code as an
experiment to just zero the low-order bit and see what that does to
the sound.

                                        BB

P.S. Yes, the whole premise of "secure music" is fundamentally
broken.  Yes, the minute someone figures the algorithm, the
watermark is gone.  Yes, converting it to an MP3 would hopelessly
destroy the watermark.  Yes, this is copy protection, and we know
that can't be made to work.  At least one story on this whole
thing says that unnamed techies associated with the SDMI
initiative pushed for this hacking contest to prove these
exact points.  Should the SDMI people actually pick some
technology to try this, I fully expect we will crack it
within a few days of having code in hand.


Current thread: