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Encryption Security

Another Audio Watermark Scheme Wins TI DSP Contest 119

Posted by timothy from the psshhhshhhsh-don't-play-this-psshhshshhh dept.
CaptainTylor writes: "Texas Instruments' DSP and Analog Design Contest Challenge is over, and the winner is a group of students from Technion, the Israel Institute of Technology, who presented yet another scheme for digital-audio watermarking, and got US$100,000 for it. Here is a Dallas Morning News article on the winners, which is of course light on the tech details. Abstracts of the winner and the other two finalists are available, but I couldn't find the full submissions. It's worth noting that the competition was not specifically about copyright protection, just about using the TI TMS320 DSP in interesting ways. Wonder how long it'll take before someone cracks this scheme..."

And speaking of schemes, cracking, audio and contests, Logic Bomb writes: "According to an article from the Associated Press, the United States National Archives are holding a contest of sorts to see if anyone can finally figure out what was erased on the infamous Watergate tape that pushed Nixon's downfall over the brink. It would be amazing to have this national mystery put to rest."
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Another Audio Watermark Scheme Wins TI DSP Contest More

Another Audio Watermark Scheme Wins TI DSP Contest

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  • If this algorithm hasn't already been cracked... (Score:3, Interesting)

    by crushinator ( 212593 ) on Thursday August 09, 2001 @01:44PM (#2117211)
    It would probably be wise to do so quickly, before the scheme is actually put into use for protecting anything copyrighted, at which point it becomes blessed with DMCA Power.

    Actually, that brings up an interesting question: Suppose someone decides today to use a copyright protection scheme which was cracked by researchers *before* the DMCA went into effect. Does it then suddenly become illegal to traffic in the so-called circumvention mechanisms? Does it become illegal to republish or redistribute the paper?

    If so, a lot of back-issues of technical journals could be considered contraband under the law. Whee!

    • If so, a lot of back-issues of technical journals could be considered contraband under the law. Whee!

      Actually, wouldn't that be an idea on how to show to the public the effects of the DMCA? Use a well-known (and bad) encryption algorithm for copyright protection, then sue some respected scientific journals that explain why the algorithm is bad (and maybe also the libraries where you find those journals) for publishing circumvention devices?

      But then again, courts would probably see a difference between code that is printed on paper and code that is saved on a computer. I guess the latter is "more executable" or something.

  • Watermarking won't work. (Score:3, Interesting)

    by r3volve ( 460422 ) on Thursday August 09, 2001 @01:23PM (#2118376)
    As far as I'm aware, there are only two options for a company intending to use a watermarking technology:

    1. Embed the watermark in the actual audio (for example, a high-frequency series of hisses throughout the song. this would enable the watermark to be present, more or less, if translated into other audio file formats)

    2. Embed the watermark in the file format

    Consumers will most likely not stand for the first option, and the second option is worthless after the watermarking scheme is cracked.

    • Learn how the technology works before you post (and get moderated up so quickly, sheesh - moderators, do some research first too). Its not as simplistic as you imply, watermarks can be embedded that are not perceptible by the human ear, yet will still be detectable even after one or more generations of loss (e.g. creating an mp3 from the original, or going Digital -> Analog and re-recording to digital). Its called steganography, and similar techniques can be used for images, e.g. allowing image watermarks that can still be detected even when images are saved in horribly lossy formats such as JPEG (see for example http://www.outguess.org/ [outguess.org])

      Watermarking should be taken seriously, this is not something you should just brush aside with one hand, this is something that (I think) is going to start being used a LOT within the next 10 years by the media cartels looking to protect their IP. Should it become common to purchase music online (which is a very likely scenario eventually, even though the RIAA is currently fighting this to protect their current monopolising of distribution channels), it should be very easy to embed a unique watermark in each individual song purchased (not unlike the Intel PIII CPU ID); while this alone would not prevent piracy directly, it does provide a very handy powerful facility for tracking pirated music - a pirated MP3 could always be tracked right back down to the specific individual who purchased it. It wouldn't take too many legal threats/fines/arrests before people became too scared to pirate music.

      Of course this isn't necessarily entirely "bad" if you assume that piracy is wrong, but there is potential for abuse (and American companies have proven time and again that if there is potential for abuse, there'll be abuse).

    • Not true, a simple way to add a watermark would be to change/not change the least significant bit according to your watermark pattern. in pcm samples over a certain threshold value. This would be nearly imperceptable (probably imperceptible to average ear) and with the original (master). digital signal you could easily extract the watermark. This is an admittedly weak way of doing it, but somebody who knows more math than me could probably come up with a similar way to watermark copies that would be harder to obfuscate.
      • No, I don't think fiddling with the least significant bit would work well as a watermarking measure. That bit is VERY likely to change when the signal goes through encoding (MP3, OGG), converting (digital -> analog -> digital), or whatever. I thought of it too, but I quickly dismissed the scheme as unpractical.

        Since they used a DSP for that scheme, it may have to do with frequencies (just an idea...). Why not a signal in some inaudible frequencies? I don't think so, it would be too easy to filter. I think it could be some frequency packing, ie, you filter certain frequencies out and mix their value into a very close frequency, close enough that the human ear won't notice it, but a machine will. It is likely to work well if you do it in the low frequency range, would I say (totally instinctively, based on my absolute ear and nothing else, so it doesn't mean much, alright -- that, and the fact high frequencies ARE left out when you encode at 11Khz). Then, to check for a watermark, you look for a pattern in the way certain given frequencies are filtered out. If the frequency at which the filter is turned on and off is of the same order of magnitude as the frequency being filtered, chances are it can't be detected through statistical analysis, especially if the frequency patterns filtered that way vary rapidly.

        But, you realize, that's pure speculation. :) More info about audio watermarking would really be appreciated, if someone is knowledgeable in this area.

  • SDMI had similar concept - cracked quickly... (Score:4, Interesting)

    by mydigitalself ( 472203 ) on Thursday August 09, 2001 @01:26PM (#2118411)
    in my *gasp* physical copy (so no, i don't know the URL) of Wired from july 2001 there was banner on the cover : THE RIAA DOESN'T WANT YOU TO SEE WHAT'S ON PAGE 61. naturally page 61 talks about a group of people accepting SDMI's challenge to crack their encryption algorthyms, which were based on watermarking.

    er, so anyway, the point is (and i think this was on /. at some point) you can check this url - scroll down a bit to get to the meat of the crack - for more information on audio watermarking and its effectivity:
    http://cryptome.org/sdmi-attack.htm [cryptome.org]

    anyway, selling media online has always been something churning around in the back of my mind and every time i come up with some sort of idea that may or may not work i, i can pretty much figure out a way to crack it.

    my conclusion is that there is no way you can encrypt this data in an uncrackable way due to the fact that at some point you have to send audio data to the sound card - and if anyone intercepts that stream or |'s it to another dev then all your effort is wasted.

    surely a viable solution would be to use hardware-based decryption using PKI. like lets say my sound card had a mobile (cell phone) like SIM card slot in it. so i buy this sound card, register with some MSP (music service provider) who supple me with a SIM card that i slot into my sound card. then i can download encrypted media (like NOT destiny's child, please!) and, tada, a workable solution.

    the first thought that has always come into my mind here is *ping* HARDWARE DONGELS. nooooo. what a success that was! but i feel this is slightly different. its not like you are having software that probes for the existance of something which can be decompiled and cracked.

    i've got a number of other great ideas on this that i've been formulating for over 3 years now, if anyone out there is interested in getting together to maybe push something like this forward (i have a lot of ideas with regards to ownership of content and so on as well - basically giving you the same "freedom" of ownership that you have with physical media), give me a shout on michael_jw_bartlett at hotmail dot com.

    of course you can always buy gold audio jacks, plug it into you sound card's output and plug the input into your cd writer... ;)

    • I can explain the weakness in this technique in 3 words: Pirate Cable descramblers
      • i have little knowledge about pirating cable signals, but surely the difference is this:

        if i buy a song from an MSP, on their servers they have an unencrypted version of the song that they encrypt with my public key and then i download it.

        in the case of cable pirating, that's a multicast signal that requires some sort of key to access. surely the signal that you are receiving is not encrypted uniquely to your device and the SIM card is not directly involved in PKI decryption of the signal.

        er i may be wrong, like i said, i know nothing about cable pirating...

    • The card you're talking about is the SoundBlaster Audigy. It encrypts PCI bus data. And works with Windows secure audio path to prevent driver rerouting. Of course, this doesn't prevent stuff under Linux or the cable attack, but still makes life hard for most people. Links:

      http://www.xbitlabs.com/news/story.html?id=9925559 37 for audigy bit
      http://msdn.microsoft.com/library/default.asp?url= /library/en-us/wmrm/htm/understandingthesecureaudi opathmodel.asp for secure audio path.

      Watch those extra spaces.

    • Here's the Wired article [wired.com].

      (don't even bother modding me up for this. It took all of thirty seconds to find it.)

      Soundbyte from the article: watermarking relies on security through obscurity. Any obsessive slashdotter will tell you that relying exclusivally on such security is a Very Bad Thing (tm).

    • of course you can always buy gold audio jacks, plug it into you sound card's output and plug the input into your cd writer


      Take it another step... don't do the decryption in the soundcard, send the encrypted stream to the speakers.

      of course then you can always just put a microphone in front the speakers
      • I need to borrow an ocsiliscope one day and run a comparison between $10 cables, and $150 cables. I have my doubts there is much difference between them. (with a fe price points between.). I'm sure at some point the result is: Spending more is not cost effective.

    • surely a viable solution would be to use hardware-based decryption using PKI

      You mean like this [intertrust.com]?

  • I Know! (Score:4, Funny)

    by Steve B ( 42864 ) on Thursday August 09, 2001 @01:41PM (#2123083)
    the United States National Archives are holding a contest of sorts to see if anyone can finally figure out what was erased on the infamous Watergate tape that pushed Nixon's downfall over the brink

    It's [EXPLETIVE DELETED] [EXPLETIVE DELETED] [EXPLETIVE DELETED] [EXPLETIVE DELETED] [EXPLETIVE DELETED] [EXPLETIVE DELETED] [EXPLETIVE DELETED] [EXPLETIVE DELETED] [EXPLETIVE DELETED] [EXPLETIVE DELETED]....

  • It's Kind Of Sad... (Score:3, Insightful)

    by Fleet Admiral Ackbar ( 57723 ) on Thursday August 09, 2001 @01:12PM (#2124598) Homepage
    ...that some of the brightest young programmers out there are turning their energies in this direction.


    The word on Free Software needs to go out to these kids, to show them that their admirable skill can help make the world a more free place. If they can program a DSP for watermarking, maybe they can help create better speech synthesis for the Stephen Hawkings of the world...

    • Well, on the flip side, watermarking could potentially be a useful way for you to lock down back up data and audio CD's that you burned yourself and own so that no one could copy (or potentially even access) the info on the CD (or DVD) without the watermarking key. I know encryption methods already exist for this sort of thing, but newer, better ones can't be bad. You know what they always say... "Build a better mouse trap, and the world will beat a path to your door."

      It's not the tool that's bad, it's how it's used that can be bad...

    • Sure, and absolutely everyone subscribes to the same left-wing philosophy as you. Why oh why would some of the brightest minds in the industry want to jump on a bandwagon that is as shaky as OSS has become and still features a questionable (at best) "pay for support" revenue model? Recent history has clearly shown what happens when the VC money runs out.

      Believe it or not, there are those to whom a relatively steady paycheck is more important than pie-eyed ideals. Not all of us are satisfied living in a dingy office at MIT.

    • Re:It's Kind Of Sad... (Score:4, Interesting)

      by Sc00ter ( 99550 ) on Thursday August 09, 2001 @01:18PM (#2152672) Homepage
      Stephen Hawkings was offered a more normal sounding speech synthesis computer, but he turned it down.

    • There's something to be said for systems level programming, API's and making programs work "nice" with the OS. But I wouldn't be caught dead with such a job. Maybe it's just the nerd in me talking, but if it ain't got math, it ain't got nothing.

      We bought computers so that we could do mathematics quicker, and I learned to program so that I could tell it what math to do.

      Windows XP, and yes, even Unix will be lost forever in the next ice age. Fast fourier transforms will be useful til the end of time.

  • I cracked it (Score:4, Funny)

    by Reckless Visionary ( 323969 ) on Thursday August 09, 2001 @01:13PM (#2128342)
    Just hold the audio up to the light, it's right there.

    • Re:I cracked it (Score:2, Insightful)

      by Anonymous Coward
      A safe bet: The 'watermarking scheme' is pretty trivial.

      TI doesn't care about the algorithm - they just want engineering students to work with TI kit, get some experienced TI users and sell heaps of TI chips.

  • Universal CDR? Engineers please respond... (Score:3, Insightful)

    by visualight ( 468005 ) on Thursday August 09, 2001 @02:03PM (#2130403) Homepage
    Is it possible to manufacture a player that is completely programmable? Like that first personal computer that came in a kit. People could buy a "blank" player and write their own firmware for it. The firmware images could be downloaded and installed so my kit player could be a cd/dvd/cdr/cdrw/something completely different. This would place TOTAL control in the hands of the "consumer" (don't you hate being called that?).

    • Well, I'm just an armchair engineer, but since you don't have a reply right now I'll chime in.

      The answer is, as always, yes and no.

      For the codecs and such, yes. You could make a programmable player and as long as you had enough cycles you could make it able to decode anything with downloaded firmware. For new media types, like CD-R vs. DVD you would need new hardware too. The optics for CD don't work on DVDs. But the DVD optics can read CDs.. so you can go backwards just like everything else in computers today. So what this gives you is a modular player unit that can accept various drive types for media, and has a programmable DSP to run the decoders on. So you could download a Ogg Vorbis decoder for your player that used to do MP3 only, for example. But you would have to buy hardware to be able to play CDs instead of just flash cards or whatever it was able to do before.

      Yes, it would give customers a lot of freedom. But it would probably cost a little more and be a little bulkier. And eaiser to break since you have peices that have to be able to come apart. Would it sell? To geeks, sure, you could make a few bucks. To joe user? Hmmm... don't know. Some would like it I'm sure. Put it in a really cool case with pretty colors as an option and you might get somewhere. If a big name like Sony built and marketed it, even better chance.

    • Re:Universal CDR? Engineers please respond... (Score:1, Informative)

      by Anonymous Coward
      It's been done..every CDR/CD/DVD/DVDRAM maker makes their own firmware..most of the components are generic off the self stuff..the problem lies in that you have to "reverse engineer" the PCB layout etc, and figure out how to program the micro-controller on the board..some companies go one up, and produce a custom ASIC...and well all know what reverse engineering gets you under the DCMA and EULAs..even for our OWN HARDWARE.

  • The Nixon contest is a trap (Score:4, Funny)

    by Beinoni ( 206765 ) on Thursday August 09, 2001 @01:21PM (#2130891)
    Anyone who recovers what Nixon erased from the tape will be sued by his estate under the DMCA for circumventing his encryption scheme. Sorry.

  • Well... (Score:5, Insightful)

    by Templar ( 14386 ) on Thursday August 09, 2001 @01:22PM (#2136567) Homepage
    No matter how unrealistic it is as a business model, copy protection is still an interesting problem, especially through watermarking.

    Inclusion of watermarking code into DSPs is inevitable. CD-R companies, for example, have been eager to embrace similar methods... try burning a SafeDisc2 protected image on a new Plextor drive. Even a perfect data source can just be blocked by hardware, by detecting patterns.

    Obviously, some companies will see a way to make a profit by getting around this. Educated consumers will buy hardware without locks.

    The question is, will Congress permit anyone to create CD-R writers (for example) in the future that do not have firmware copy protection.

    I hope the DMCA was an anomaly, and not an example of things to come.
    • Even if every single CD-R writer company did embed watermarking code in hardware, how long do you think it would take for someone to come up with a hardware solution? Think Playstation and modchips.
      • Except that for CD drives, it may work pretty well.

        CD drives have to be very precisely balanced. If you were to attempt to modify one, its likely that the next thing you'll do is head to the store to buy a new drive because you completely fux0red the old one.

        For an experiment, put a wad of tape on the outside of your CD drive: It'll sound like a jet airplane taking off. (I did this once to try to dampen the noise of my 48x drive, and it had the completely opposite effect. After my ears stopped bleeding, I figured out why that wasn't such a good idea :)

        Tim

    • SD2 is broken, badly. (Score:4, Informative)

      by eddy ( 18759 ) on Thursday August 09, 2001 @02:44PM (#2123038) Homepage Journal

      try burning a SafeDisc2 protected image on a new Plextor drive.

      No problem. The PlexWriter PX-W2410A [cdrinfo.com] does perfect Safedisc 2 copies, at least with the firmware shipped to reviewers.

      Of course, SD2 is pretty much broken if you take into consideration BetaBlocker [geocities.com], a program you can use to 'fix' a SD2-protected image prior to burning. Works with any burner.

    • Inclusion of watermarking code into DSPs is inevitable.

      Well, a DSP is a microprocessor which likes to add and multiply for real-time applications. I would expect a DSP to be able to watermark as much as an Athlon can. The impressive thing is that they're students and now I have an extreme urge to incorporate a TMS320C5410 in my car's ABS system.

      Has anyone else noticed the amount of junk mail comming from TI is extremely high? I ask them for one data sheet and I get seminar invitations and catalogs in my mail every day...
    • And then they'll order drives from overseas. When will Congress realize that they can't control an interntational, non personal (you can't extradite the internet) entity? The issue is that Americans have become stupid. Lawyers and corporations are more involved in government than citizens, and therefore, the rights of citizens are being raped.
    • try burning a SafeDisc2 protected image on a new Plextor drive. Even a perfect data source can just be blocked by hardware, by detecting patterns.

      Please elaborate. Are you saying that if I burn original material that I created using a new Plextor CD drive that it will nonetheless watermark it or otherwise munge my data?

      The question is, will Congress permit anyone to create CD-R writers (for example) in the future that do not have firmware copy protection.

      The Congress, nor any other municipality in the U.S., can only restrict what we allow it to. It is not up to Congress to 'permit' it. I know that you simply used a convenient phrase, but it's important to remember this key distinction. The U.S. system allows government to do only what we allow it to get away with, otherwise it must keep it's grubby, greedy hands off.

      People have rights, government has limited powers. Too bad more of us don't remember this.

  • good to see... (Score:4, Funny)

    by ravrazor ( 69324 ) on Thursday August 09, 2001 @01:45PM (#2136643)
    ...that canada's still represented...although the university of waterloo is getting weirder and weirder. take a bunch of nerds, put them in a small town with a beer festival and this is the result, i guess.

    anybody (from UW or otherwise) got an abstract for this one?

    Canada
    University of Waterloo
    Intelligent Motion Control Using the TMS320LF2407 Applied to a Six-Legged Walking Robot

  • Cracking it... (Score:5, Funny)

    by ackthpt ( 218170 ) on Thursday August 09, 2001 @01:44PM (#2136731) Homepage Journal
    Wonder how long it'll take before someone cracks this scheme..."

    Maybe they actually wrote the crack first, then reverse engineered it.

  • Design Contests (Score:3, Insightful)

    by Pinball Wizard ( 161942 ) on Thursday August 09, 2001 @01:27PM (#2138364) Homepage Journal
    Isn't this just a way to get students to do low-cost engineering work for you?

    These things should be sponsored by universities or non-profit organizations like the ACM, not companies. I'd imagine the winning solutions are worth far more than the prizes offered.

  • I'm sure most of you know this, but let me back up for a minute. One technology tries to keep you from making copies; the other technology assumes you will make copies but will be caught.

    The purpose of copy protection is to prevent you from copying something, regardless of legality, illegality, or your rights under the fair use doctrine. All together now, "DUH!"

    The purpose of a digital watermark is to identify a data file as authentic, or alternatively to identify its source. Such a watermark will NOT stop you from copying the file, but it may be able to identify that you were the source of the copy. Now, there are several problems with digital audio watermarks, one of which is the difficulty of embedding one without unacceptable loss of sound quality.

    Both copy protection and watermarking can theoretically be bypassed by the "play through good speakers and record the output with good microphone and then you have the option of digitally encoding." Such digital recording will in all likelihood be of lower audio quality than the "protected" original, however it will be free of the copy protection and/or watermark. So which is more important, the ability to copy, or the sound quality?

  • They need voices from a tape un-erased? Sounds like a job for . . . MOVIE OS! [userfriendly.org]

    Brought to you by the people that gave you the Infinite Sharpness filter for Photoshop (find those completely sharp faces buried in fuzzy films) and the Internet Welcome Screen.

  • From their competition (Score:2, Informative)

    by murph1e ( 117881 )
    I'm a member of the team from Rice University [rice.edu] that went up against the guys from the Technion in the DSP Challenge finals. You can whine all you want about wheter audio watermarking is the right thing to do, but you can't deny that these guys put together a *really* cool system.

    Their presentation to the judges was very impressive (we presented first, and all I could think while watching theirs was "we're screwed..."). They demonstrated both the addition and detection of a watermark for pre-recorded and live audio. A couple of times, they played out loud just the watermark. It was pretty garbled, but you could definitely make out the content of the original audio. They did it for both vocal and instrumental music; both times, you could make out the lyrics and melody of the original sound. And when combined with the original, the watermark was inaudible (as promised).

    But the most impressive part of all is that it was all done in real-time. They watermarked the audio from a local radio station as it was being broadcast, playing both the resulting watermark and watermarked audio with virtually no delay.

    I told them in Dallas, but I'll say it again- Congratulations on winning. You guys were definitely worthy competition. With any luck, we'll face each other again next time around.
    -patrick

  • Already Cracked! (Score:3, Insightful)

    by cnelzie ( 451984 ) on Thursday August 09, 2001 @01:17PM (#2152269) Homepage

    I just figured out how to crack it! Take great quality audio reproduction equipment (Speakers) and then some very high quality audio collection devices (Microphones) and put it all in a proper sound room, or box.

    For right and left channel sound you will need to have at least two speakers and at least two microphones and some way of merging the two recordings.

    It might be a little far from perfect, but so are MP3's and the sound from the "Cracked" watermarked music.

    Wait a minute... Since Sklyarov was arrested for creating a tool to break a protection scheme, does this mean that speakers and microphones are now illegal?

    I suppose it is all how you interpret the DMCA...

    --
    .sig seperator
    --
    • roger that....am breaking out the reel-to-reel right now.

      will send you a copy of the original on 8 track from prison.

    • The idea of the watermark is that it's hidden in the audio signal, so it's there even if you go from digital to analogue or reproduce it in eny way. A type of watermark is already used for the DVD-audio format.

      Many HiFi specialists dosn't like this since they want a totally clean signal. The watermark is probebly not possible to hear on most HiFi systems, maby not on eny system.

      But if you are one of those who has paid 6000£ for just the signal cables (what are those maid of enyway, solid gold? :p ), then you wouldn't want some unessery crap to the signal, would you?

      Even if it shouldn't be possible to hear the watermark it must still be in the range of frequencys that humans can hear, otherwise most speakers wouldn't be able to reproduce it.

      So this would mean that if you only played the watermark you would offcource hear it.

    • Why bother with the speakers and mic. Once the MP3 is converted back to analog couldn't you just pipe the analog signal back in and convert it back to digital then store it as the new file?

      ...Oh wait if that works maybe using analog signals is illegal as well.
      • Why bother with the speakers and mic. Once the MP3 is converted back to analog couldn't you just pipe the analog signal back in and convert it back to digital then store it as the new file?
        Although this approach will not remove the watermark, it WILL allow you to play the audio on a different player (one that does not check for watermarks).

        No matter what the regulators do, there will always be a software hack (non-standard audio player, etc) to ignore the watermark. The only way to ensure that the watermark can be detected is with a special sound card. Even if the regulators come up with such a thing, a discerning customer (aka geek) will always opt for the non-restrictive hardware. Therefore, the only way this could become truly ugly is if the government outlawed "normal" sound cards and forced hardware manufacturers to stop making them.

        If that happens, we've got bigger problems to worry about...

        -- Brett

      • Oh wait didn't consider the previous post about watermarks...guess that takes care of my so well thought out hack.
    • Why bother with speakers and a microphone? Connect your sound card's (stereo system's, whatever) sound output jack directly to the microphone or input jack. No fuss, no mess.
    • I bet you haven't really done this.

      I was a demonstration of an audio watermarking system that did _Exactly_ this. Except it was in a very noisy confereence room. And the speakers were really shitty. And so was the microphone.

      The watermark was inperceptible to me. But not to the computer with the microphone.

      This demonstration was given by someone at Microsoft Research.

      I don't know if this was the exact research group, but you can read about some of the watermarking work going on at MSR here:

      http://research.microsoft.com/scripts/pubs/view.as p?TR_ID=MSR-TR-99-05 [microsoft.com]
    • All the comments about the watermark still existing even through analog/digital conversions because it's a part of the audio signal that we can't hear, don't take into account that this could be bypassed by using a filter that filters out any part of the audio signal outside the ranges of human hearing. Yes?
      • nope.

        First - digital audio contains VERY little frequencies that can't be heard by humans - what would be the point of encoding audio that can't be heard? For dogs? c.f. Nyquist sampling limit. Compact discs are sampled at 45Khz, so 22.5Khz is the upper limit of the sound that they can repro. That is outside of human range, but not by much.

        Second - generally these watermarking schemes are very sophisticated. A simple band limiting/passing filter isn't going to do it. You need to do know the specifics of how it's encoded to remove it.... not that it can't be done (c.f. the guys that broke the SDMI challenge). Watermarks contain 'echo's' of themselves, time dependant bits, time independant bits, using one sound to mask another (a human wouldn't hear it), etc etc etc. They're pretty sophisticated.

        About 4 years (?) ago at MIT i saw a demonstration of a watermarking scheme where they played music out of some speakers. They held a microphone up to the speaker, and their computer spit out what the watermark was. So the people who keep saying that they'd re-record watermarked audio this way can only do it if they have a recording device that doesn't obey/enforce the watermark. The fact that they've gone Digital->Analog and possibly back to digial doesn't matter a single bit.
      • I don't think that is quite right. I think the reason it can't be heard is because of its short duration. The watermark is distributed throughout the file in small chunks or whatever. Each chunk doesn't last long enough or is not repeated enough in sequence for our ear to realize it is there.
    • Nice job on the "post without reading or thinking" maneuver, mate!

      See, it's a *watermark*. Now, what does "watermark" mean? Well, in this case, a watermark is data embedded in an audio signal that can do such things as identify the copyright holder of that signal.

      Re-record the signal and guess what? The watermark is still there!

      Joy!

      Well, with your skills, maybe you can join the Slashdot Special Olympics! Start working on your crapflooding, and maybe you can win multiple medals!

    • Not even close (Score:3, Informative)

      by furiousgeorge ( 30912 )
      Lets be clear here....... these watermarks are in the AUDIO - not in the specific digial representation. They are designed to survive thru generation loss, going from digital->analog->digital again (and maybe going form CD -> MP3 encoding back to CD) or any of a thousand variations.

      If i make a recording that is a voice saying "DO NOT DUPLICATE" and every recording device on the market 'listens' for that sound, and if it hears it refused to record, the fact that you play via analog an re-record won't matter. The only way around it would be to remove the "DO NOT DUPLICATE". Now what these schemes do is exactly that - except they do lots of complicated and tricky ways to hide "DO NOT DUPLICATE", along with trying to encode it in the most robust fashion even if the signal gets modified. And in the same vein, they try to hide the signal in such a way that removing it would cause too much undesireable in the underlying music. The Stanford guys that broke the SDMI challege showed that it was possible to remove, but removing it ISN'T simple.

      In your above 'cracking' example, it would only work if your recording device (not the microphones, the actual machine that persisted the music coming in) didn't respect/obey the watermark.

      You haven't cracked anything. You've only demonstrated that you haven't a clue on how this technology works, nor a simple basic understanding of signal processing theory. If you ask Santa nicely he might bring you a spectrum analyzer for chrismas.....

    • I just figured out how to crack it! Take great quality audio reproduction equipment (Speakers) and then some very high quality audio collection devices (Microphones) and put it all in a proper sound room, or box.

      Why go that far, just tap it off the output of the D/A converter, or better yet (if you're a pro) tap it off the input to the D/A converters. 8)

  • Hmm (Score:1)

    by ez76 ( 322080 )
    Personally, I'd like to see the brightest young minds continue to have access to well-produced commercial music.

  • Cause they copied it! (Score:4, Funny)

    by SirSlud ( 67381 ) on Thursday August 09, 2001 @01:19PM (#2152663) Homepage
    what was erased on the infamous Watergate tape that pushed Nixon's downfall over the brink. It would be amazing to have this national mystery put to rest

    Actually, I heard the blank spot was just noise introduced by a top-secret CIA funded copy-protection scheme from the era. ;)

    Hey, at least we got some of the tape! If all this copy-protection shit had been introduced 30 years ago, we wouldn't have the tape AT ALL.

    Heehee.
    • "Actually, I heard the blank spot was just noise introduced by a top-secret CIA funded copy-protection scheme from the era. ;) "

      Wouldn't that mean that the attempts to hear what's there would violate the DMCA?

      I think we're in trouble.

  • what a horrible idea (Score:5, Funny)

    by Chundra ( 189402 ) on Thursday August 09, 2001 @01:33PM (#2152750)
    Dammit. If there's one thing I truly hate, it's getting water in my ear. It sloshes around and makes everything sound muffled. Try as I might, there's nothing I can do to get it out of there, so eventually I give up. Then, late at night, I'll be lying in bed and this unexpected stream of warm water trickles onto my pillow. Suddenly I can hear again! Out of curiosity, I get up, turn on the light and see just a few drops of ear fluid on the pillow. I think to myself, "Wow, such a tiny watermark made such a big difference".

    And they want us to PAY for that? I think not!

  • 1) Get a team of 10 audio researchers
    2) Get one persone working on a watermarking technique
    3) Get the other 9 try to break the technology
    4) If (technology broken) then goto 2) with another researcher

    ...and loop forever until you realize that you can't make a watermark that cannot be broken.

  • Wonder (Score:4, Funny)

    by Anonymous Coward on Thursday August 09, 2001 @01:10PM (#2153320)
    "Wonder how long it'll take before someone cracks this scheme.."

    I wonder how long it'll take before someone gets arrested for cracking this scheme...
    • I wonder how long before someone makes a Beowulf cluster of TMS320 DSPs...

      Smoke crack, rather than crack, the jail time is less, eh?

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