On Monday, I attended the 8th ACM DRM workshop. Here are my feedbacks on this workshop.

There were two invited talks.
KAHN Robert (from CNRI) presented The role of identifiers in information access . The talk was about the Digital Object Architecture (DOA). The idea behind that is to redraw Internet from a communication centric system to a digital object centric system. Every digital object would be identified by a unique handle and servers/proxies would resolve it and provide the actual location of repository (reminds you something :Wink:?, Kahn is behind TCP/IP). This is what is used for DOI.
The link with DRM? The message was that it is important to separate the terms and conditions (expressed as metadata) from the actual enforcement. I fully agree. . His attempt to apply it to the Broadcast Flag was more dubious.

The second invited speaker was YACOV Yacobi. He is the lead of Microsoft’s anti-piracy group. He presented Content Identification He tackled three issues: piracy versus counterfeiting, new DRM and economics of fight against counterfeiters. His distinction between pirated goods and counterfeited goods seemed not extremely good to me. A counterfeited good is a physical good that looks like the original and is sold at about the same price. Thus, the sorting is mainly on the price.
His new DRM approach was the use of media hashing (what we currently call fingerprinting or perceptual hash). Clearly, he was not aware of the state of the art in the field, both about existing solutions, and approaches like the one proposed by Philips many years ago.
In the last part, he presented a complex modeling of economics to determine the optimal effort in counterstriking counterfeiters. It would have been more interesting to focus all his presentation only on this topic.

About the other papers:
JIN Hei (IBM) presented Adaptive traitor tracing for anonymous attack. The starting point is the sequence keys traitor tracing scheme of AACS. It was an extensive analysis on how many movies you had to retrieve to safely incriminate one infringer within a non cooperating coalition. The figures are still very high. As we stated many years ago, sequence keys will probably never be useful in AACS. Furthermore, the analysis assumes that the infringer does not collude content with other members. Would I be an attacker, this is what I would do. Nevertheless, nice theoretical work using probability.

YUNG M. (Microsoft) presented Public-key traitor tracing from efficient decoding and unbounded enrollment . A traitor tracing scheme based on El Gamal. I will let Marc JOYE comment :Wink:

JAMKHEDAR Pramod presented Formal Modeling of Rights. He proposed a scheme that should encompass any Rights Expression Language. Compared to the work of GUTH or CHONG, there is the addition of obligations inside the model. Obligations are external conditions that have to be accomplished prior to granted this action.

DOERR (with Ton KALKER) presented Design rules for interoperable domains – Controlling content dilution and content sharing . It was a presentation of two interesting concepts of CORAL: the rights token (a REL that is independent from the DRMs) and management of domains. The most interesting part was the ideas on how to control the size an dilution. He proposed three mechanisms: proximity, cardinals, and time-out. I think that we did not dare to embed time-out for contents within DVB-CPCM. I am not sure that people would appreciate.

Discussions were extremely interesting. Long discussion with the representative of EFF (but that is another story)

And of course, I presented my paper A Four Layer Model for Security of DRM

Heileman G. and Jamkhedkar P. are regular contributors for ACM DRM workshop. For many years, they have presented a paper at each workshop. An their papers are worthwhile.

Last year, they presented an interesting http://portal.acm.org/citation.cfm?id=1314287. It analyzed the different possible strategies for Vendor and Consumer using the game theory. The model was rather simplistic. Thus, there was no big surprise in the outcomes especially when analyzing the baseline game (section 2). Would DRM be unbreakable, Vendor should always sell protected content. For Vendor, it is important decrease the utility of downloaded content versus sold content. Only common sense.

The paper becomes more interesting with section 3 when it analyzes the sub-games. What does the consumer do with content and how Vendor reacts. One outcome is that the higher the penalty, the less Consumers Vendor has to sue. The interesting part is the description of a distribution mechanism with a trust valuation that defines the cost of the content and the associated bonuses. This is a trend that was initiated for many years by Philips labs based on the use of forensic watermark.

I have always problem with that philosophy because it relies on the rather strong assumption that the trust evaluation will work. I have many doubts about that, especially with B2C traitor tracing. Today, you have only limited number of sources on P2P networks, and they do not collude. Let’s now suppose that Consumers understand that they may cheat if either they collude or they issue more instances of sources just to dilute the system… I do not even speak about attacking the reputation system (look in electronic auctions).

Nevertheless, game theory seems an interesting tool to explore strategies. We may expect to see papers in the future with more complex models. I would like to see one which would differentiate authors from vendors/distributors and vendors from authorities.

Michael Lesk, from Rutgers University, attempted to answer why online music stores sell to each customer at the same price. Interestingly, every song is sold at the same price, regardless of its performer. The price of the corresponding CD varies depending on the artist’s fame. Online stores have good profiling of Alice. Thus, they could easily propose a personalized price slightly lower than the price she would be ready to pay. According to Lesk, it is not a privacy issue but a feeling of resentment that frightens the sellers.

One alternative that make price differentiation acceptable is versioning. People accept that a hard-bounded book is more expensive then a paper back. People may accept to pay more for a content they will be able to view several times, than for a content that they will view only once. This is the role of DRM. DRM may allow to decrease the average price by offering different versions. Unfortunately, today DRM is not used for that, probably because it is simpler and safer for merchants to offer one unique price.

Reference of the paper
LESK Michael, Digital Rights Management and Individualized Pricing, in IEEE Security & Privacy, May/June 2008