Cheun Ngen Chong

Comparing Logic-Based and XML-Based Rights Expression Languages

Several rights expression languages (RELs) have been proposed to describe licenses governing the terms and conditions of content access. In this field XrML and ODRL play a prominent role. Both languages are powerful yet complex. In this paper we propose a way of analysing RELs and we apply it to ODRL, XrML and to LicenseScript, a REL we propose. In addition, we test these languages against a number of example scenarios. These examples bring new insights, and shed new light on some of the limits of XrML and ODRL.

Security Attributes Based Digital Rights Management

Most real-life systems delegate responsibilities to different authorities. We apply this idea of delegation to a digital rights management system, to achieve high flexibility without jeopardizing the security. In our model, a hierarchy of authorities issues certificates that are linked by cryptographic means. This linkage establishes a chain of control, identity-attribute-rights, and allows flexible rights control over content. Typical security objectives, such as identification, authentication, authorization and access control can be realized. Content keys are personalized to detect illegal super distribution. We describe a working prototype, which we develop using standard techniques, such as standard certificates, XML and so forth. We present experimental results to evaluate the scalability of the system. A formal analysis demonstrates that our design is able to detect a form of illegal super distribution.

License protection with a tamper-resistant token

Content protection mechanisms are intended to enforce the usage rights on the content. These usage rights are carried by a license. Sometimes, a license even carries the key that is used to unlock the protected content. Unfortunately, license protection is difficult, yet it is important for digital rights management (DRM). Not many license protection schemes are available, and most if not all are proprietary. In this paper, we present a license protection scheme, which exploits tamper-resistant cryptographic hardware. The confidentiality and integrity of the license or parts thereof can be assured with our protection scheme. In addition, the keys to unlock the protected content are always protected and stored securely as part of the license. We verify secrecy and authentication aspects of one of our protocols. We implement the scheme in a prototype to assess the performance.

StreamTo : streaming content using a tamper-resistant token

Stream To uses a tamper resistant hardware token to generate the key stream needed to decrypt encrypted streaming music. The combination of a hardware token and streaming media effectively brings tried and tested Pay-TV technology to the Internet. We present two prototype implementations with a performance assessment, showing that the system is both effective and efficient.