At EuroCrypt '95, Stadler, Piveteau and Camenish introduced the concept of fair blind signatures to prevent the misuse of blind signature schemes by criminals. Recently, Hwang, Lee and Lai claimed that Stadler et al.'s first fair blind signature scheme cannot meet the untraceability property of the blind signature schemes. However, this letter will demonstrate that Hwang et al.'s claim is incorrect and Stadler et al.'s first scheme still holds the untraceability property.

Digital Rights Management (DRM) ensures that the usage of digital media adheres to the intentions of the copyright holder and prevents the unauthorized modification or distribution of media. Due to the widespread adoption of digital content use, DRM has received a fair amount of attention and has seen implementation in many commercial models. Although many DRM schemes have been introduced in the literature, they still suffer from some security issues and may not guarantee the quality of performance. In this paper, we propose a trust-distributed DRM model to provide improvements for realistic DRM environments to bring more functionality to users. We use the features of the smart cards to provide an option of anonymity for the consumer while continuing to protect the rights of the copyright holder and the financial interests of the media industry. We also classify the security criteria of DRM systems and show that our proposed smart card based DRM scheme satisfies all of these criteria.