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[WM]: Re: Another use for steganography
"Subtracting" it from the track is challenging.
It would be one thing if you digitally mixed in the the recording bit-for-bit as it appeared on the CD. But by playing it in the
background, a very large number of deviations and errors are introduced (which is good) by way of the particular speakers and
decoders you used to play back the music, the acoustics of the room in which the music was played and of course the properties of
the microphone picking up the music. Consequently, I believe it would be quite challenging, even given a well-identified piece, to
remove all reasonable traces of music from such an overlaid composition.
As I pragmatist, I would encourage you to go for the simpler solution.
Trying to pick obscure works to use is a false comfort; if you believe your enemies are intent enough to try these complex
subtractions to subvert your words, a simple search for a piece of music will be the smallest of their challenges; instead you would
need to have a machine that dynamically composed music with some form of secret key known only to you and the machine and seeded
based on the start time of the recording.
-D
On 1/25/06, Jon Roland <jon.roland@constitution.org> wrote:
> Yes, and that's what I've been doing. However, if the falsifier wants
> to use a
> recording of my voice made with a music overlay he has only to
> identify the piece
> and subtract it from the track before beginning his work. I've been
> using obscure
> electronic pieces that would be difficult to identify.
>
> I am looking for something more subtle that he would have trouble
> detecting or
> subtracting, such that even if he used samples of my voice to
> fabricate a track,
> something of the watermark would survive and be detectable by a
> computer program
> that would produce a report that would be convincing to a court, more
> so than a
> perhaps subjective opinion that the background music shows signs of
> editing.
>
> David Weekly wrote:
> > Jon,
> >
> > Sorry for taking a month to get back to you on this. I guess you
> > slipped through my email cracks. :)
> >
> > You've brought up an interesting application of watermarking that I
> > had not considered; detecting the continuity of a recording. This
> > could be fairly tricky to intersperse with the recording in a subtle
> > way if perceptual coding is used, but background music seems a very
> > clever mechanism - wouldn't it be sufficient to play a piece that
> > had no looping parts or repeated sections? That would seem to get
> > you 99% of the way to where you wanted to go.
> >
> > -D
> >
> >
> > On 12/16/05, Jon Roland <jon.roland@constitution.org> wrote:
> >
> >>I am seeking an application for steganography: Production of a
> >>soundtrack,
> >>probably in the form of a music CD, that could be played in the
> >>background during
> >>a taped interview with a subject, that could be used to reveal if
> >>the taped words
> >>of the subject are used to compose a false "recording" to be used
> >>against him. The
> >>idea would be to be able to run the altered "recording" through a
> >>computer
> >>analysis program that would reveal in a way convincing to laypersons
> >>(such as
> >>members of a jury) that the recording presented as "evidence" is in
> >>fact
> >>falsified, by editing or sampling the original recorded words of the
> >>subject. It
> >>should be able to show gaps, interpolations, changes of order or
> >>inflection, and
> >>other changes that would be introduced in such a fabrication.
> >>
> >>The CD should be easy to use, such as by playing it in continuous
> >>loop mode on an
> >>ordinary portable CD player at a low volume.
> >>
> >>Are you aware of anyone who has done anything like this, or who
> >>might make
> >>available such a CD, and software to analyze it, for a reasonable
> >>fee? Preferred
> >>platform for the software is Linux.
>
> --
>
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