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Just remember: when you buy so-called "Secure" Digital Media, you support Digital Restrictions Management, or DRM. Boycott the "Secure" Digital Media Initiative if you care about Fair Use.

This sounds to be like you are not allowed to let anyone other than yourself use the CD in any way. If you are playing the CD yourself, and someone else walks into the room and hears it, does that count?

No, I think it's more like, "If you distribute a decoder/ripper, make a t-shirt out of it, or come up with some way around copy-protected technology with minimal features so that people with disabilities can use it. And god forbid you encourage someone to do those things! (oh wait, that's not the right link - here it is)

I wonder if Slashdot can legally be held liable for people who post stuff like this, "encouraging" us to "reproduce" the "Content". Since when did music become "Content" with a capital C?

First they ignore you, then they laugh at you, then they fight you, then you win. -- Ghandi

I have a feeling they will use a combination of video watermarking and steganography to allow copyright holders to mark any video as their own. Of course, like sdmi, it won't last long.

Persuant to the DMCA, we probably won't ever hear about it. Maybe, we need to help these guys.

The specification also states that "any Content stored on the PD [portable device] shall be SDMI Protected Content."[4] I interpret this to mean that if unprotected content (i.e. mp3 files) are uploaded to an SDMI-compliant device, that device is required to place SDMI restrictions on that content before it is stored.

-k

[1] http://www.sdmi.org/download/port_device_spec_part 1.pdf

[2] "SDMI Portable Device Specification, Part 1", version 1, p14.

[3] ibid., p31.

[4] ibid., p14.

Aside from the (questionable) joy of explaining cryptography to suits and explaining licensing requirements to geeks (Harry Fox helps throw a real monkey wrench in there, administering rights for song-writers), one of the things that came up time and time again was anti-trust issues.

SMEI and WMG were well-aware that together they represented about 30% of the market (they split that up, flip-flopping every year over who has the most based on who had bigger hits). Their expectation was that a joint venture between them would attract BMG, Universal, EMI and whoever was number six at the time. Then independents would simply have to fish or cut bait and join up as well.

Everyone was very careful to avoid using words and phrases like "controlling", "domination", etc. at least in written materials. People would verbally joke that they needed to make sure those words weren't written down, in case they ever got subpoena'ed for anti-trust, but everyone knew that the objective was making the HBO of electronic music distribution. You see, they recognized that HBO had the movie companies by the short and curlies as far as cable distribution of films went, and didn't want the same to happen to them in a new media distribution - the film companies have been worrying about this for themselves for electronic distribution for a couple of years now.

Of course, Napster beat them to it, so they beat on Napster legally. One of the funniest things about the timing of these things for me was SDMI being announced just after MP3 hit the cover of Time Magazine, when I'd been working on it for years prior. And of course they got the DMCA passed in the meantime, making cracking even the stupidest of copy control schemes illegal. Of course, every crypto expert they talked to at the time (myself included) emphasized that no scheme was foolproof and you should be sure to design the system to minimize damage in the case of a crack. Being powerful executives with lobbyists on retainer, a legal solution was obvious.

So, all in all, I'm pleasantly amused that the music companies got just a bit too eager and slipped in one phrase too many.....

Yes, but all this presupposes that you will be allowed to transfer the digital copy to, say, a CD once you download it. As it stands right now (correct me if I'm wrong), it is illegal, or it will soon be technologically prevented, to make a CD containing your favorite songs. Even though Mac ads in Wired and elsewhere show hip youngsters doing it.

Once again, so I am clear (as I am certainly not clear about this!):

Is it legal to burn a CD of your favorite songs via ripping them from your CD and writing them to another? If it is legal, how far away are we from the realization of the SDMI (RIAA wet) 'dream' of encrypted music that won't rip or burn?

20 April 2001. Thanks to Anonymous
From cryptome.org

[Letter, 3 pp.]

MATTHEW J. OPPENHEIM, ESQ.
Address illegible
RIAA

April 9, 2001

Professor Edward Felton
Department of Computer Science
Princeton University
Princeton, NJ 08544

Dear Professor Felten,

We understand that in conjunction with the 4th International Information Hiding Workshop to be held April 25-29, 2001, you and your colleagues who participated in last year's Secure Digital Music Initiative ("SDMI") Public Challenge are planning to publicly release information concerning the technologies that were included in that challenge and certain methods you and your colleagues developed as part of your participation in the challenge. On behalf of the SDMI Foundation, I urge you to reconsider your intentions and to refrain from any public disclosure of confidential information derived from the Challenge and instead engage SDMI in a constructive dialogue on how the academic aspects of your research can be shared without jeopardizing the commercial interests of the owners of the various technologies.

As you are aware, at least one of the technologies that was the subject of the Public Challenge, the Verance Watermark, is already in commercial use and the disclosure of any information that might assist others to remove this watermark would seriously jeopardize the technology and the content it protects.1 Other technologies that were part of the Challenge are either likewise in commercial use or could be could be utilized in this capacity in the near future. Therefore, any disclosure of information that would allow the defeat of those technologies would violate both the spirit and the terms of the Click-Through Agreement (the "Agreement"). In addition, any disclosure of information gained from participating in the Public Challenge would be outside the scope of activities permitted by the Agreement and could subject you and your research team to actions under the Digital Millennium Copyright Act ("DCMA").

____________________

1 The Verance Watermark is currently used for DVD-Audio and SDMI Phase I products and certain portions of that technology are trade secrets.

We appreciate your position, as articulated in the Frequently Asked Questions document, that the purpose of releasing your research is not designed to "help anyone impose or steal anything." Further more, you participation in the Challenge and your contemplated disclosure appears to be motivated by a desire to engage in scientific research that will ensure that SDMI does not deploy a flawed system. Unfortunately, the disclosure that you are contemplating could result in significantly broader consequences and could directly lead to the illegal distribution of copyrighted material. Such disclosure is not authorized in the Agreement, would constitute a violation of the Agreement and would subject your research team to enforcement actions under the DMCA and possibly other federal laws.

As you are aware, the Agreement covering the Public challenge narrowly authorizes participants to attack the limited number of music samples and files that were provided by SDMI. The specific purpose of providing these encoded files and for setting up the Challenge was to assist SDMI in determining which of the proposed technologies are best suited to protect content in Phase II products. The limited waiver of rights (including possible DMCA claims) that was contained in the Agreement specifically prohibits participants from attacking content protected by SDMI technologies outside the Public Challenge. If your research is released to the public this is exactly what could occur. In short, you would be facilitating and encouraging the attack of copyrighted content outside the limited boundaries of the Public Challenge and thus places you and your researchers in direct violation of the Agreement.

In addition, because public disclosure of your research would be outside the limited authorization of the Agreement, you could be subject to enforcement actions under federal law, including the DMCA. The Agreement specifically reserves any rights that proponents of the technology being attacked may have "under any applicable law, including, without limitation, the U.S. Digital Millennium Copyright Act, for any acts not expressly authorized by their Agreement." The Agreement simply does not "expressly authorize" participants to disclose information and research developed through participating in the Public challenge and such disclosure could be the subject of a DMCA action.

We recognize and appreciate your position, made clear throughout this process, that it is not your intention to engage in any illegal behavior or to otherwise jeopardize the legitimate commercial interests of others. We are concerned that your actions are outside the peer review process established by the Public Challenge and setup by engineers and other experts to ensure the academic integrity of this project. With these facts in mind, we invite you to work with the SDMI Foundation to find a way for you to share the academic components of your research while remaining true to your intention to not violate the law or the Agreement. In the meantime, we urge you to withdraw the paper submitted for the upcoming Information Hiding Workshop, assure that it is removed from the Workshop distribution materials and destroyed, and avoid a public discussion of confidential information.

Sincerely,

[Signature]

Matthew Oppenheim, Secretary
The SDMI Foundation

cc: Mr. Ira S. Moskowitz, Program Chair, Information Hiding Workshop, Naval Research Laboratory
Cpt. Douglas S. Rau, USN, Commanding Officer, Naval Research Laboratory
Mr. Howard Ende, General Counsel of Princeton
Mr. Edward Dobkin, Computer Science Department Head of Princeton

[Paper, 15 pp.]

Reading Between the Lines:
Lessons from the SDMI Challenge
Scott A. Craver1, John R McGregor1, Min Wu1, Bede Liu1,
Adam Stubblefield2, Ben Swartzlander2, Dan S. Wallach2,
Drew Dean3, and Edward W. Felten4 1 Dept. of Electrical Engineering, Princeton University
2 Dept. of Computer Science, Rice University
3 Computer Science Laboratory, Xerox Palo Alto Research Center
4 Dept. of Computer Science, Princeton University

Abstract. The Secure Digital Music Initiative is a consortium of parties interested in preventing piracy of digital music, and to this end they are developing architectures for content protection on untrusted platforms. SDMI recently held a challenge to test the strength of 4 watermarking technologies, and 2 other security technologies. No documentation explained the implementations of the technologies, and neither watermark embedding nor detecting software was directly accessible to challenge participants. We nevertheless accepted the challenge, and learned a great deal about the inner workings of the technologies. We report on our results here.

The Secure Digital Music Initiative (SDMI), a consortium of music-industry companies, is working to develop and standardize technologies that give music publishers more control over what consumers can do with recorded music that they buy. SDMI has been a somewhat secretive organization, releasing little information to the public about its goals, deliberations, and technology.

In September 2000, SDMI announced a "public challenge" in which it invited members of the public to try to break certain data-encoding technologies that SDMI had developed [3]. The challenge offered a valuable window into SDMI, not only into its technologies but also into its plans and goals. We decided to use the challenge to learn as much as we could about SDMI. This paper is the result of our study.1 Section 2 presents an overview of the HackSDMI challenge. Section 3 analyzes the watermark challenges. Section 4 analyzes the non-watermark challenges. Finally, we present our conclusions in section 5.

____________________

1 The SDMI challenge offered a small cash payment to be shared among everyone who broke at least one of the technologies and was willing to sign a confidentiality agreement giving up all rights to discuss their findings. The cash prize amounted to the price of a few days of time from a skilled computer security consultant, and it was to be split among all successful entrants, a group that we suspected might be significant in size. We chose to forgo the payment and retain our right to publish this paper.

The SDMI challenge extended over roughly a three-week period, from September 15, 2000 until October 8, 2000. The challenge actually consisted of six sub-challenges, named with the letters A through F, each involving a different technology developed by SDMI. We believe these challenges correspond to submissions to the SDMI's Call for Proposals for Phase II Screening Technology [4]. According to this proposal, the watermark's purpose is to restrict an audio clip which is compressed or has previously been compressed. That is, if the watermark is present an audio clip may yet be admitted into an SDMI device, but only if it has not been degraded by compression. For each challenge, SDMI provided some information about how a technology worked, and then challenged the public to create an object with a certain property. The exact information provided varied among the challenges. We note, though, that in all six cases SDMI provided less information than a music pirate would have access to in practice.

2.1 Watermark Challenges

Four of the challenges (A, B, C, and F), involved watermarking technologies, in which subtle modifications are made to an audio file, to encode copyright control information without perceptible change in how the file sounds. Watermarks can be either robust or fragile. Robust watermarks are designed to survive common transformations like digital-to-audio conversion, compression and decompression, and the addition of small amounts of noise to the file. Fragile watermarks do not survive such transformations, and are used to indicate modification of the file. For each of the four watermark challenges, SDMI provided three files:

- File 1: an unwatermarked song;

- File 2: File 1, with a watermark added; and

- File 3: another watermarked song.

The challenge was to produce a file that sounded just like File 3 but did not have a watermark -- in other words, to remove the watermark from File 3.

SDMI provided an on-line "oracle" for each challenge. Entrants could email a file to the oracle, and the oracle would tell them whether their submission satisfied the challenge, that is, whether it contained no detectable watermark while still sounding like File 3. Entrants were given no information about how watermark information was stored in the file or how the oracle detected watermarks, beyond the information that could be deduced from inspection of the three provided files.

2.2 Challenges D and E

Challenge D concerned a technology designed to prevent a song from being separated from the album in which it was issued. Normally, every Compact Disc contains a table of contents, indicating the offsets and lengths of each audio track, followed by the audio data itself. Challenge D adds an "authenticator" track (approximately 50ms of very quiet audio,) a digital signature derived from the table of contents, which is supposed to be difficult to compute for an arbitrary CD. Challenge D is discussed in more detail in Section 4.1.

Challenge E involved a technology similar to D, but one which would be immune the obvious attack on technology D, in which one compiled an unauthorized CD with the same table of contents as an authorized one, for which the authenticator track is given. Unfortunately, this challenge was constructed in a way that made it impossible to even start analyzing the technology. SDMI provided an oracle for this challenge, but unfortunately provided no music samples of any kind, so there was no way to determine what the oracle might be testing for.

Given these facts, we decided not to analyze Challenge E. It is discussed briefly in Section 4.2.
3 The Watermarking Schemes

In this section, we describe our attack(s) on each of the four watermark challenges (A,B,C,F). Our success was confirmed by emails received from SDMI's oracles. Fig. 1. The SDMI watermark attack problem. For each of the four watermark challenges, Sample-1, sample-2, and sample-3 are provided by SDMI sample-4 is generated by participants in the challenge and submitted to SDMI oracle for testing.

Figure 1 provides an overview of the challenge goal. As mentioned earlier, there are three audio files per watermark challenge: an original and watermarked version of one clip, and then a watermarked version of a second clip, from which the mark is to be removed. All clips were 2 minutes long, sampled at 44.1kHz with 16-bit precision.

The reader should note one serious flaw with this challenge arrangement. The goal is to remove a robust mark, while these proposals appear to be Phase II watermark screening technologies [4]. As we mentioned earlier, a Phase II screen is intended to reject audio clips if they have been compressed, and presumably compression degrades a fragile component of the watermark. An attacker need not remove the robust watermark to foil the Phase II screen, but could instead repair the modified fragile component in compressed audio. This attack was not possible under the challenge setup.

3.1 Attack and Analysis of Technology A

A reasonable first step in analyzing watermarked content with original, unmarked samples is differencing the original and marked versions in some way. Initially, we used sample-by-sample differences in order to determine roughly what kinds of watermark- ing methods were taking place. Unfortunately, technology A involved a slowly varying phase distortion which masked any other cues in a sample-by-sample difference. We ultimately decided this distortion was a pre-processing separate from the watermark, in part because undoing the distortion alone did not foil the oracle.

The phase distortion nevertheless led us to attempt an attack in which both the phase and magnitude change between sample 1 and sample 2 is applied to sample 3. This attack was confirmed by SDMI's oracle as successful, and illustrates the general attack approach of imposing the difference in an original-watermark pair upon another media clip. Here, the "difference" is taken in the FFT domain rather than the time domain, based on our suspicions regarding the domain of embedding. Note that this attack did not require much information about the watermarking scheme itself, and conversely did not provide much extra insight into its workings.

A next step, then, is to compute the frequency response H(w) = W(w)/O(w) of the watermarking process for segments of audio, and observe both |H(w)| and the corresponding impulse response h(t). If the watermark is based on some kind of linear filter, whose properties change slowly enough relative to the size of a frame of samples, then this approach is ideal.

Figure 2 illustrates one frequency response and impulse response about 0.3 seconds into the music. These responses are based on FFTs of 882 samples, or one fiftieth second of music. As can be clearly seen, a pair of sinusoidal ripples are present within a certain frequency band, approximately 8-16Khz. Ripples in the frequency domain are indicative of echoes in the time domain, and a sum of sinusoids suggested the presence of multiple echoes. The corresponding impulse response h(t) confirms this. This pattern of ripples changes quite rapidly from frame to frame.

Thus, we had reason to suspect a complex echo hiding system, involving multiple time-varying echoes. It was at this point that we considered a patent search, knowing enough about the data hiding method that we could look for specific search terms, and we were pleased to discover that this particular scheme appears to be listed as an alternative embodiment in US patent number 05940135, awarded to Aris corporation, now part of Verance [5]. This provided us with little more detail than we had already discovered, but confirmed that we were on the right track, as well as providing the probable identity of the company which developed the scheme. It also spurred no small amount of discussion of the validity of Kerckhoffs's criterion, the driving principle in security that one must not rely upon the obscurity of an algorithm. This is, surely, doubly true when the algorithm is patented. Fig. 2. A short-term complex echo. Above, the frequency response between the watermarked and original music, taken over 1/50 second, showing a sinusoidal ripple between 8 and 16 KHz. Below, the corresponding impulse response. The sinusoidal pattern in the frequency domain corresponds to a pair of echoes in the time domain.
The most useful technical detail provided by the patent was that the "delay hopping" pattern was likely discrete rather than continuous, allowing us to search for appropriate frame sizes during which the echo parameters were constant. Data collection from the first second of audio showed a frame size of approximately 882 samples, or 1/50 second. We also observed that the mark did not begin until 10 frames after the start of the music, and that activity also existed in a band of lower frequency, approximately 4-8 Khz. This could be the same echo obscured by other operations, or could be a second band used for another component in the watermarking scheme. A very clear ripple in this band, indicating a single echo with a delay of about 34 samples, appears shortly before the main echo-hopping pattern begins.

The next step in our analysis was the determination of the delay hopping pattern used in the watermarking method, as this appeared to be the "secret key" of the data embedding scheme. It is reasonable to suspect that the pattern repeats itself in short order, since a watermark detector should be able to find a mark in a subclip of music, without any assistance initially aligning the mark with the detector's hopping pattern. Again, an analysis of the first second revealed a pattern of echo pairs that appeared to repeat every 16 frames, as outlined in figure 3. The delays appear to fall within six general categories, each delay approximately a multiple of 1/4 millisecond. The exact values of the delays vary slightly, but this could be the result of the phase distortion present in the music. Fig. 3. The hypothesized delay hopping pattern of technology A. Here two stretches of 16 frames are illustrated side-by-side, with observed echoes in each frame categorized by six distinct delays: 2, 3, 4, 5, 6 or 7 times 0.00025 sec. Aside from several missing echoes, a pattern appears to repeat every 16 frames. Note also that in each frame the echo gain is the same for both echoes.

The reader will also note that in apparently two frames there is only one echo. If this pattern were the union of two pseudorandom patterns chosen from six possible delay choices, two "collisions" would be within what is expected by chance.

Next, there is the issue of the actual encoded bits. Further work shows the sign of the echo gain does not repeat with the delay-hopping pattern, and so is likely at least part of an embedded message. Extracting such data without the help of an original can be problematic, although the patent, of course, outlines numerous detector structors which can be used to this end. We developed several tools for cepstral analysis to assist us in the process. See [2] for in introduction to cepstral analysis; Anderson and Petitcolas [1] illustrate its use in attacks on echo hiding watermark systems.

With a rapidly changing delay, normal cepstral analysis does not seem a good choice. However, if we know that the same echo is likely to occur at multiples of 16/50 of a second, we can improve detector capability by combining the information of multiple liftered2 log spectra.

____________________

2 in accordance with the flopped vocabulary used with cepstral analysis, "liftering" refers to the process of filtering data in the frequency domain rather than the time domain. Similarly, "quefrencies" are frequencies of ripples which occur in the frequency domain rather than the time domain.

Three detector structures are shown in figure 4. In all three, a collection of frames are selected for which the echo delays are believed to be the same. For each, the liftered log of an FFT or PSD of the frame is taken. In the first two structures, we compute a cepstrum, for each frame, then either average their squared magnitudes, or simply their squares, in hopes that a spike of the appropriate quefrency will be clear in the combination. The motivation for merely squaring the spectral coefficients comes from the observation that a spike due to an echo will either possess a phase of theta or theta + pi for some value theta. Squaring without taking magnitudes can cause the echo phases to reinforce, whilst still permitting other elements to combine destructively. Fig. 4. Three cepstral detector structures. In each case we have a collection of distinct frames, each believed to possess echoes of the same delay. The first two compute cepstral data for each frame, and sum their squares (or squared magnitudes) to constructively combine the echo signal in all frames. The third structure illustrates a method for testing a hypothesized pattern of positive and negative gains, possibly useful for brute-forcing or testing for the presence of a known "ciphertext."

In the final structure, one cepstrum. is taken using a guess of the gain sign for each suspect frame. With the correct guess, the ripple should be strongest, resulting in the largest spike from the cepstral detector. Figure 5 shows the output of this detector on several sets of suspect frames. While this requires an exponential amount of work for a given amount of frames, it has a different intended purpose: this is a brute-forcing tool, a utility for determining the most probable among a set of suspected short strings of gain signs as an aid to extracting possible ciphertext values. Fig. 5. Detection of an echo. A screenshot of our CepstroMatic utility shows a combination of 4 separate frames of music, each a fiftieth of a second long, in which the same echo delay was believed to exist. Their combination shows a very clear ripple on the right, corresponding to a clear cepstral spike on the left. This is a single echo at a delay of 33 samples, the delay suggested for these intervalus by the hypothesized delay-hopping pattern.

Finally, there is the issue of what this embedded watermark means. Again, we are uncertain about a possible signalling band below 8Khz. This could be a robust mark, signalling presence of a fragile mark of echoes between 8 and 16 KHz. The 8-16KHz band does seem like an unusual place to hide robust data, unless it does indeed extend further down, and so this could very easily be hidden information whose degredation is used to determine if music has already been compressed.

Of course, knowledge of either the robust or fragile component of the mark is enough for an attacker to circumvent the scheme, because one can either remove the robust mark, or repair or reinstate the fragile mark after compression has damaged it. As mentioned earlier, this possible attack of repairing the fragile component appears to have been ruled out by the nature of the SDMI challenge oracles. One must wait and see if real-world attackers will attempt such an approach, or resort to more brute methods or oracle attacks to remove the robust component.

3.2 Attack on Challenge B

We analyzed samp1b.wav and samp2b.wav using short-time FFT. Shown in Fig. 6 are the two FFT magnitudes for 1000 samples at 98.67 sec. Also shown is the difference of the two magnitudes. A spectrum notch around 2800Hz is observed for some segments of samp2b.wav and another notch around 3500Hz is observed for some other segments of samp2b.wav. Similar notches are observed in samp3b.wav. The attack fills in those notches of samp3b.wav with random but bounded coefficient values. We also submitted a variation of this attack involving different parameters for notch description. Both attacks were confirmed by SDMI oracle as successful. Fig. 6. Technology-B: FFT magnitudes of samp1b.wav and samp2b.wav and their difference for 1000 samples at 98.67 sec.

3.3 Attacks on Challenge C

By taking the difference of samp1c.wav and samp2c.wav, bursts of narrowband signal are observed, as shown in Fig. 7. These narrow band bursts appear to be centered around 1350 Hz. Two different attacks were applied to Challenge C. In the first at- tack, we shifted the pitch of the audio by about a quartertone. In the second attack, we passed the signal through a bandstop filter centered around 1350Hz. Our submissions were confirmed by SDMI oracle as successful. In addition, the perceptual quality of both attacks has passed the "golden ear" testing conducted by SDMI after the 3-week challenge. Fig. 7. Challenge-C: Waveform of the difference between samp1c.wav and samp2c.wav.

3.4 Attack on Challenge F

For Challenge F, we warped the time axis, by inserting a periodically varying delay. The delay function comes from our study on Technology-A, and was in fact initially intended to undo the phase distortion applied by technology A. Therefore the perceptual quality of our attacked audio is expected to be better than or comparable to that of the audio watermarked by Technology-A. We also submitted variations of this at- tack involving different warping parameters and different delay function. They were confirmed by SDMI oracle as successful.
4 The Non-Watermark Technologies

The HackSDMI challenge contained two "non-watermark" technologies. Together, they appear to be intended to prevent the creation of "mix" CDs, where a consumer might compile audio files from various locations to a writable CD. This would be enforced by universally embedding SMDI logic into consumer audio CD players.

4.1 Technology D

According to SDMI, Technology D was designed to require "the presence of a CD in order to 'rip' or extract a song for SDMI purposes." The technology aimed to accomplish this by adding a 53.3 ms audio track (four blocks of CD audio), which we will refer to as the authenticator, to each CD. The authenticator, combined with the CD's table of contents (TOC), would allow a SDMI device to recognize SDMI compliant CDs. For the challenge, SDMI provided 100 different "correct" TOC-authenticator pairs as well as 20 "rogue tracks". A rogue track is a track length that does not match any of the track lengths in the 100 provided TOCs. The goal of the challenge was to submit to the SDMI oracle a correct authenticator for a TOC that contained at least one of the rogue tracks.

The oracle for Technology D allowed several different query types. In the first type, an SDMI provided TOC-authenticator combination is submitted so a that user can "understand and verify the Oracle." According to SDMI, the result of this query should either be "admit" for a correct pair or "reject" for an incorrect pair. When we attempted this test a SDMI-provided pair, the oracle responded that the submission was "invalid." After verifying that we had indeed submitted a correct pair, we attempted several other submissions using different TOC-authenticator pairs as well as different browsers and operating systems3. We also submitted some pairs that the oracle should have rejected; these submissions were also declared "invalid." Though we alerted SDMI to this problem during the challenge, the oracle was never repaired. For this reason, our analysis of Technology D is incomplete and we lack definitive proof that it is correct. That having been said, we think that what we learned about this technology, even without the benefit of a correctly functioning oracle, is interesting.

____________________

3 Specifically, Netscape Navigator and Mozilla under Linux, Netscape Navigator under Windows NT, and Internet Explorer under Windows 98 and 2000.

Analyzing the Signal Upon examination of the authenticator audio files, we discovered several patterns. First, the left and right channels contain the same information. The two channels differ by a "noise vector" u, which is a vector of small integer values that range from -8 and 8. Since the magnitude of the noise is so small, the noise vector does not significantly affect the frequency characteristics of the signal. The noise values appear to be random, but the noise vector is the same for each of the 100 provided authenticator files. In other other words, in any authenticator file, the difference between the left and right channels of the ith sample is a constant fixed value u[i]. This implies that the noise vector u does not encode any TOC-specific information.

Second, the signal repeats with a period of 1024 samples. Because the full signal is 2352 samples long, the block repeats approximately 1.3 times. Similarly to the left and right channels of the signal, the first two iterations of the repeating signal differ by a constant noise vector v. The difference between the ith sample of the first iteration and the ith sample of the second iteration differ by a small (and apparently random) integer value v[i] ranging from -15 to 15. In addition, v is the same for each of the provided authenticator files, so v does not encode any TOC-specific information.

Third, the first 100 samples and last 100 samples of the full signal are faded in and faded out, respectively. This is illustrated in Figure 8. The fade-in and fade-out are meaningless, however, because they simply destroy data that is repeated in the middle of the file. We conjecture that this fade-in and fade-out are included so that the audio signal does not sound offensive to a human ear. Fig. 8. In a Technology D Authenticator, the signal fades in, repeats, and fades out.

Extracting the Data Frequency analysis on the 1024 sample block shows that almost all of the signal energy is concentrated in the 16-20kHz range, as shown in Figure 9. We believe this range was chosen because these frequencies are less audible to the human ear. Closer examination shows that this l6-20kHz range is divided up into 80 discrete bins, each of which appears to carry one bit of information. As shown in Figure 10, these bits can be manually counted by a human using a graph of the magnitude of signal in the frequency domain. Fig. 9. Magnitude vs. Frequency of Technology D Authenticator

Fig. 10. Individual Bits From a Technology D Authenticator

Close inspection and pattern matching on these 80 bits of information reveals that there are only 16 bits of information repeated 5 times using different permutations. using the letters A-P to symbolize the 16 bits, these 5 permutations are described in Figure 11. ABCDEFGHIJKLMNOP
OMILANHGPBDCKJFE
PKINHODFMJBCAGLE
FCKLGMEPNOADJBHI
PMGHLECAKDONIFJB Fig. 11. The encoding of the 16 bits of data in Technology D

Because of the malfunctioning oracle, we were unable to determine the function used to map TOCs to authenticators, but given an actual SDMI device, it would be trivial to brute force all 216 possibilities. Likewise, without the oracle, we could not determine if there was any other signal present in the authenticator (e.g., in the phase of the frequency components with nonzero magnitude).

For the moment, let us assume that the hash function used in Technology D has only 16 bits of output. Given the number of distinct CDs available, an attacker should be able to acquire almost, if not all, of the authenticators. We note that at 9 kilobytes each, a collection of 65,536 files would fit nicely on a single CD. Many people have CD collections of 300+ discs, which by the birthday paradox makes it more likely than not that there is a hash collision among their own collection.

Our results indicated that the hash function used in Technology D could be weak or may have less than 16 bits of output. In the 100 authenticator samples provided in the Technology D challenge, there were 2 pairs of 16-bit hash collisions. We will not step through the derivation here, but the probability of two or more collisions occurring in n samples of X equally likely possibilities is:

If the 16-bit hash function output has 16 bits of entropy, the probability of 2 collisions occurring in n = 100 samples of X = 216 possibilities is 0.00254 (by the above 1.5 equation). If X ~ 211.5, the chances of two collisions occurring is about even. This suggests that either 4 bits of the 16-bit hash output may be outputs of functions of the other 12 bits or the hash function used to generate the 16-bit signature is weak. It is also possible that the challenge designers purposefully selected TOCs that yield collisions. The designers could gauge the progress of the contestants by observing whether anyone submits authenticator A with TOC B to the oracle, where authenticator A is equal to authenticator B. Besides the relatively large number of collisions in the provided authenticators, it appears that there are no strong biases in the authenticator bits such as significantly more or less 1's than 0's.

4.2 Technology E

Technology E is designed to fix a specific bug in Technology D: the TOC only mentions the length of each song but says nothing about the contents of that song. As such, an attacker wishing to produce a mix CD would only need to find a TOC approximately the same as the desired mix CD, then copy the TOC and authenticator from that CD onto the mix CD. If the TOC does not perfectly match the CD, the track skipping functionality will still work but will only get "close" to track boundaries rather than reaching them precisely. Likewise, if a TOC specified a track length longer than the track we wished to put there, we could pad the track with digital silence (or properly SDMI-watermarked silence, copied from another valid track). Regardless, a mix CD played from start to end would work perfectly. Technology E is designed to counter this attack, using the audio data itself as part of the authentication process.

The Technology E challenge presented insufficient information to be properly studied. Rather than giving us the original audio tracks (from which we might study the unspecified watermarking scheme), we were instead given the tables of contents for 1000 CDs and a simple scripting language to specify a concatenation of music clips from any of these CDs. 'Me oracle would process one of these scripts and then state whether the resulting CD would be rejected.

While we could have mounted a detailed statistical analysis, submitting hundreds or thousands of queries to the oracle, we believe the challenge was fundamentally flawed. In practice, given a functioning SDMI device and actual SDMI-protected content, we could study the audio tracks in detail and determine the structure of the watermarking scheme.
5 Conclusion

In this paper, we have presented an analysis of the technology challenges issued by the Secure Digital Music Initiative. Each technology challenge described a specific goal (e.g., remove a watermark from an audio track) and offered a Web-based oracle that would confirm whether the challenge was successfully defeated.

We have reverse-engineered and defeated all four of their audio watermarking technologies. We have studied and analyzed both of their "non-watermarking" technologies to the best of our abilities given the lack of information available to us and given a broken oracle in one case.

Some debate remains on whether our attacks damaged the audio beyond standards measured by "golden ear" human listeners. Given a sufficient body of SDMI-protected content using the watermark schemes presented here, we are confident we could refine our attacks to introduce distortion no worse than the watermarks themselves introduce to the the audio. Likewise, debate remains on whether we have truly defeated technologies D and E. Given a functioning implementation of these technologies, we are confident we can defeat them.

Do we believe we can defeat any audio protection scheme? Certainly, the technical details of any scheme will become known publicly through reverse engineering. Using the techniques we have presented here, we believe no public watermark-based scheme intended to thwart copying will succeed. Other techniques may or may not be strong against attacks. For example, the encryption used to protect consumer DVDs was easily defeated. Ultimately, if it is possible for a consumer to hear or see protected content, then it will be technically possible for the consumer to copy that content.

References

1. R. J. ANDERSON, AND F. A. P. PETITCOLAs. On the limits of steganography. IEEE Journal of Selected Areas in Communications 16,4 (May 1998),474-481.

2. R. P. BOGERT, M., AND J. W. TUKEY. The quefrency alanysis of time series for echoes: Cepstrum, pseudo-autocovariance, cross-ceptsrum and saphe-cracking. In Proceedings of the Symposium on Time Series Analysis (Brown University, June 1962), pp. 209-243.

3. R. PETROVIC, J. M. WINOGRAD, K., AND E. METOIS. Apparatus and method for encoding and decoding information in analog signals, Aug. 1999. US Patent No 05940135 http://www.delphion.com/details?pn=US05940135__.

4. SECURE DIGITAL MUSIC INITIATIVE. Call for Proposals for Phase II Screening Technology, Version 1.0, Feb. 2000. http://www.sdmi.org/download/FRWG00022401-Ph2_CFPv 1.0.PDF.

5. SECURE DIGITAL MUSIC INITIATIVE. SDMI public challenge, Sept. 2000. http://www.hacksdmi.org.

For alternatives, look at Archos 6000.

Cheaper. And can double as a portable USB hard drive! Don't know if the USB protocol is open though, but I don't think archos need to guard the specs like Creative do.

But, as this article makes fairly clear, studio-quality productions are now within easy reach of anyone with a PC and a modicum of talent (some would say even the talent is optional). If you want cool new music from the best trackers or the best independent musicians make sure you keep those watching over your rights financially healthy.

Troll version: screw the RIAA/MPAA/Disney/Time Warner bunnies and join the EFF today!

Q - Can SDMI-compliant devices play MP3 files? A - Yes. SDMI-compliant devices will be able to play all existing digital formats; it is up to the manufacturer of each device to choose which particular formats to support. The only content SDMI-compliant devices will not play is illegally copied SDMI music beginning in Phase 2. Unlike non-SDMI devices, SDMI devices can also be upgraded to play new music released in the future in new SDMI-compliant formats. And many SDMI portable devices will be able to play music that is digitally downloaded in new, protected formats right away.

9. Q - Will the watermark technology chosen for Phase 1 interfere with existing CD players? A - There are hundreds of millions of CD players in the marketplace and nothing being done within SDMI will in any way limit consumers' ability to use those machines with existing and new CDs.

These two statements imply that, while "Phase 1" does not harm fair use rights, "Phase 2" will include technologies that restrict the playing of a "illegally copied" SDMI file. The implicit assumption, in restricting Question 9, above, to both "Phase 1" SDMI, and "existing CD players" is that eventually "Phase 2" SDMI and future CD players will work together to disable copying of music.

The copyright industry has long held the assumption that "fair use" is only a defence against claims of copyright infringement, and does not constitute a right in itself. In their view, all copying is illegal, unless specifically authorized by a court (in dismissing a infringement suit), or by the copyright owner. So, even if a consumer wishes to copy music to give to a friend, or excerpt a segment for a brief review (all examples of fair use), he or she will be stymied by "anti-piracy" features in the SDMI-2 spec.

CSS, SDMI, and like technologies act as contracts, to be enforced by compliant devices. These enforcement mechanisms will eventually have technological ability to prevent copying, and Congress has passed a number of laws (17 US Code 1201 et seq) that attach legal penalties to the circumvention of these pseudo contracts.

If and when SDMI becomes widespread, various lobyists from the RIAA, MPPA et al. will propose that the importation and manufacture of devices that do not recognize SDMI be banned (as contributing to piracy). (DAT players and VHS VCRs are already required to implement "Serial Copy Management System" and "Color stripe" respectively.

So yes, SDMI is something to be feared. It's akin to having an RIAA lawyer living in your computer.

How is their Minidisc crippled? I hadn't heard of that.

Of course, that this is the same company that brought us the Music Clip MP3 player... one of those nifty devices that asks you to convert all of your MP3s to some "secure" format. Their PlayStation uses specially-formatted CDs that can't be copied. Aren't they a member of SDMI too?

For what it's worth, my ears aren't that sensitive. How many people out there are saying, "the audio quality of these CDs is really driving me to insanity, when oh when will someone come up with a better format?"

Thank you for contacting us. We appreciate your interest in the public challenge of proposed SDMI screening technologies. The challenge closed at noon on October 8, 2000,
and we are no longer accepting submissions.

If you have previously submitted a challenge, we should already have
contacted you. If we have not yet contacted you, or you have other
questions, please e-mail us at contact@hacksdmi.org. If you need more
information about SDMI in general, please check the website www.sdmi.org.

Thank you again for your interest.

It really doesn't matter whether SDMI is hacked before or after music starts being released with either the Phase 1 or Phase 2 watermark. However, all the watermark can do is identify a track, and give some sort of guidelines of the rights the 'licensee' has. ** The whole plan hinges on software that pays attention to the watermark. ** SDMI's plan is simple: Divide and conquer. The 'big' software companies pay attention to the watermark because they are rich targets for lawsuits, plus they want to use popular (i.e. big five label) content. After the big software companies have signed up, SDMI can start going after the small players. Having a link to Gnutella on your site might make you a target! Let's get anonymous, reliable transfer and hosting for open source audio software going! Chris Owens San Carlos, CA

It really doesn't matter whether SDMI is hacked before or after music starts being released with either the Phase 1 or Phase 2 watermark. However, all the watermark can do is identify a track, and give some sort of guidelines of the rights the 'licensee' has. ** The whole plan hinges on software that pays attention to the watermark. ** SDMI's plan is simple: Divide and conquer. The 'big' software companies pay attention to the watermark because they are rich targets for lawsuits, plus they want to use popular (i.e. big five label) content. After the big software companies have signed up, SDMI can start going after the small players. Having a link to Gnutella on your site might make you a target! Let's get anonymous, reliable transfer and hosting for open source audio software going! Chris Owens San Carlos, CA

Broken links all around.
I really don't get it. Why send out press releases and letters that 'point' to a site that still under construction???

Sent to info@sdmi.org:

Dear Mr. Chiariglione,

While I am not quite as eloquent as Don Marti, I do wish to inform you that I won't be participating in the "hack the sdmi" initiative (it's *crack*, anyway, not *hack*). As a seasoned computer professional with considerable experience in cryptography (specifically, a port of PGP to Apple's now-defunct Newton), I would normally enjoy such a challenge. I'm afraid, however, that SDMI is a misguided initiative, hostile to me as a consumer and unacceptable as a means of "protecting" the media I currently enjoy.

Actually, I probably *will* work on or paricipate in an effort to crack the SDMI, but you'll need to check Slashdot or 2600 for the results of my work. Thank you.

Also, there are SDMI Phase 1-compliant devices out there, this one for example, coming to the US in November, for which I wrote some of the PC software.

And no, I don't know anything about how to hack the Verance watermark, we just got a module from them.

I beleive your thinking of the SDMI and DMAT. (WARNING: That second link goes straight into the belly of the beast!) Read up there if you want to find out more of what the Music Industry has planned for us consumers.

I was reading their web site and I found...

"SDMI Compliant" in the flash presentation. Oh my.

As we all know, the Secure Digital Music Initiative (Their site is at http://www.sdmi.org) can't do anything; anyone heard "bit-by-bit" before? And there's always those nice dummy wave-output audio devices....

<sigh>

Silly RIAA.


I'm guessing though that Sony's player (due **Winter** 2000) won't be restricted to just SDMI; their web site seemed to make that reasonably clear.

Before one can know if SDMI does the right thing, one must have a clear picture of what the right thing is. One thing the recorded music publishers have neglected for years is that they were only incidentally selling atoms. Really, they were always selling licenses.

I have here a brand-new shrink wrapped CD. Copyright mark and one warning on the outside - "unauthorized duplication is violation of applicable laws". Pop the wrap. Disc itself has the same print. Liner notes have copyright statements, same warning.

So here's an odd thing - I've bought some atoms and a license, but I haven't got a clear picture of that license.

I took a quick pass at smdi.org and wasn't too informed by it. So I buzzed over to riaa.org where this item is a pointer on The Digital Performance Right in Sound Recordings Act of 1995 I should run over and read the acts, but I haven't yet. "Ignorance of the law is no excuse..."

Music licensing is fiercely complex anyway - many organizations can "own" an aspect of the same performance. Making rights visible would go a long way towards making SDMI restrictions comprehensible - and maybe getting rid of some restrictions.

Henry Troup

hwt@igs.net

"It appears you can't move the music files around on your disk. They get stored in an encrypted form and if you try and reorganize them other than through the SDMI compliant software, they go boom!"

That's about it. Playing your music on a SDMI device? Forget about playing it on a non-SDMI device. What's even worse, is that if "circumstances arise" in which the SDMI player's security gets cracked (a la DVD), then the company making the affected product has to make another one. (Clause 10.4)

Additionally, the RIAA gets to crack open the devices to ensure that they're SDMI-compliant. Well, they don't get to, but they can appoint an outside expert *hack* *cough* to do the work. (Clause 10.5)

"It appears that storing your music on read-only media like CDR will not be possible."

According to the SDMI FAQ, you can, but I'm skeptical.

"It appears SDMI is a security standard only and doesn't guarantee interoperability between SDMI devices from multiple manufacturers."

Bingo. Hell, I doubt a lot of manufacturers would be inclined to produce SDMI-complaint products, as it would cause too much confusion between companies that can't agree on a standard.

"It looks like SDMI might be one of those 'standards' that can't be distributed as open source without its security being broken."

Bingo again. DVD anyone?

For more information, check out MP3 Newswire's SDMI information page.

"It appears you can't move the music files around on your disk. They get stored in an encrypted form and if you try and reorganize them other than through the SDMI compliant software, they go boom!"

That's about it. Playing your music on a SDMI device? Forget about playing it on a non-SDMI device. What's even worse, is that if "circumstances arise" in which the SDMI player's security gets cracked (a la DVD), then the company making the affected product has to make another one. (Clause 10.4)

Additionally, the RIAA gets to crack open the devices to ensure that they're SDMI-compliant. Well, they don't get to, but they can appoint an outside expert *hack* *cough* to do the work. (Clause 10.5)

"It appears that storing your music on read-only media like CDR will not be possible."

According to the SDMI FAQ, you can, but I'm skeptical.

"It appears SDMI is a security standard only and doesn't guarantee interoperability between SDMI devices from multiple manufacturers."

Bingo. Hell, I doubt a lot of manufacturers would be inclined to produce SDMI-complaint products, as it would cause too much confusion between companies that can't agree on a standard.

"It looks like SDMI might be one of those 'standards' that can't be distributed as open source without its security being broken."

Bingo again. DVD anyone?

For more information, check out MP3 Newswire's SDMI information page.

"It appears you can't move the music files around on your disk. They get stored in an encrypted form and if you try and reorganize them other than through the SDMI compliant software, they go boom!"

That's about it. Playing your music on a SDMI device? Forget about playing it on a non-SDMI device. What's even worse, is that if "circumstances arise" in which the SDMI player's security gets cracked (a la DVD), then the company making the affected product has to make another one. (Clause 10.4)

Additionally, the RIAA gets to crack open the devices to ensure that they're SDMI-compliant. Well, they don't get to, but they can appoint an outside expert *hack* *cough* to do the work. (Clause 10.5)

"It appears that storing your music on read-only media like CDR will not be possible."

According to the SDMI FAQ, you can, but I'm skeptical.

"It appears SDMI is a security standard only and doesn't guarantee interoperability between SDMI devices from multiple manufacturers."

Bingo. Hell, I doubt a lot of manufacturers would be inclined to produce SDMI-complaint products, as it would cause too much confusion between companies that can't agree on a standard.

"It looks like SDMI might be one of those 'standards' that can't be distributed as open source without its security being broken."

Bingo again. DVD anyone?

For more information, check out MP3 Newswire's SDMI information page.

• Anticipated Technical Functionality of Phase 2 Screening of Digital Audio Content
• SDMI Portable Device Specification - Part 1, Version 1.0 (PDWG99070802)
• Amendment 1 to the SDMI Portable Device Specification - Part 1, Ver 1 (PDWG99092302)
• Guide to SDMI Portable Device Specification - Part 1, Version 1.0
• Int erim Phase 1 SDMI Trademark License and Compliance Agreement

• Anticipated Technical Functionality of Phase 2 Screening of Digital Audio Content
• SDMI Portable Device Specification - Part 1, Version 1.0 (PDWG99070802)
• Amendment 1 to the SDMI Portable Device Specification - Part 1, Ver 1 (PDWG99092302)
• Guide to SDMI Portable Device Specification - Part 1, Version 1.0
• Int erim Phase 1 SDMI Trademark License and Compliance Agreement

• Anticipated Technical Functionality of Phase 2 Screening of Digital Audio Content
• SDMI Portable Device Specification - Part 1, Version 1.0 (PDWG99070802)
• Amendment 1 to the SDMI Portable Device Specification - Part 1, Ver 1 (PDWG99092302)
• Guide to SDMI Portable Device Specification - Part 1, Version 1.0
• Int erim Phase 1 SDMI Trademark License and Compliance Agreement

• Anticipated Technical Functionality of Phase 2 Screening of Digital Audio Content
• SDMI Portable Device Specification - Part 1, Version 1.0 (PDWG99070802)
• Amendment 1 to the SDMI Portable Device Specification - Part 1, Ver 1 (PDWG99092302)
• Guide to SDMI Portable Device Specification - Part 1, Version 1.0
• Int erim Phase 1 SDMI Trademark License and Compliance Agreement

• Anticipated Technical Functionality of Phase 2 Screening of Digital Audio Content
• SDMI Portable Device Specification - Part 1, Version 1.0 (PDWG99070802)
• Amendment 1 to the SDMI Portable Device Specification - Part 1, Ver 1 (PDWG99092302)
• Guide to SDMI Portable Device Specification - Part 1, Version 1.0
• Int erim Phase 1 SDMI Trademark License and Compliance Agreement

http://www.sdmi.org/

Just so we know what we're talking about. From that site:

• Anticipated Technical Functionality of Phase 2 Screening of Digital Audio Content
• SDMI Portable Device Specification - Part 1, Version 1.0 (PDWG99070802)
• Amendment 1 to the SDMI Portable Device Specification - Part 1, Ver 1 (PDWG99092302)
• Guide to SDMI Portable Device Specification - Part 1, Version 1.0
• Interim Phase 1 SDMI Trademark License and Compliance Agreement

On a related note, SDMI, which exists solely to manage copy protection for music, managed to let the certificate expire on their secure web server. Remember, these guys want to manage the keys to all the audio content in the world. Here's their current certificate:

This Certificate belongs to:
www.sdmi.org
EMS
Global Integrity
La Jolla, California, US
This Certificate was issued by:
Secure Server Certification Authority
RSA Data Security, Inc.
US
Serial Number: 1D:37:FE:F6:B9:A4:C0:91:41:B1:F9:D7:1C:43:A2:A4
This Certificate is valid from Wed Jan 06, 1999 to Fri Jan 07, 2000
Certificate Fingerprint: DF:EE:C6:82:A9:E2:8E:27:91:5F:8E:ED:6D:06:0D:FB

After a while, of free reign, where anybody can pirate music, some people are starting to look around and asking questions... and one major question is if anything is happening to prevent mp3 distribution.

Well, there isn't much people can do. There have been a few attempt to prevent people from pirating music, but not many succesful ones. It seems that this person was to set an example, to show that people aren't allowed to pirate music. And, it didn't work either.

here's where i start to go off-topic
But, the RIAA has also tried to prevent people from pirating music. So far, they've just tried to sue companies, such as Diamond, for releasing the Diamond Rio. They also have attempted to sue napster, since they have a client which "created a forum that lets online users trade unauthorized music files directly from their PCs".

Of course, if you haven't heard, there is then SDMI, which is promoted by the RIAA. SDMI stands for Secure Digital Music Initiative. It is an attempt to prevent piracy of music altogether.

Yes thats right. The plan is that you can't use the sony thingie for distribution. It's a SDMI sortha solution(hey you can sing this! mmmm... free music).


LINUX stands for: Linux Inux Nux Ux X