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Modern DRM system not only emphasizes the protection of copyrights, but also aims to support specific business use models for the digital contents. Group distribution is a kind of newer business distribution model that would allow to purchase the digital contents by an group, such as a family or an organization etc. It makes convenient for consumer, but how to use the rights of group flexibly and securely has not been solved yet. In this paper, we propose two kinds of rights delegation models, m2m and m2c for group distribution and also give a formal definition for these models. We propose authenticate method for consumer and personalize content encryption key to detect illegal distribution. Finally, we describe security license distribution mechanism for these models.

The traditional superdistribution model supports the contents distribution only between users. In this paper, we are presenting the enhanced superdistribution model in order to support the fair use of contents as including the content distribution within family domain as well. Family domain consists of user owned devices. In addition that we propose the license model, using information of distribution history for the secure management of the enhanced superdistribution. The history information is composed of device identifiers. The use of history information makes the contents used only in granted superdistribution and family domain. The history information is protected with asymmetric encryption method to prevent from privacy information leakage. The enhanced superdistribution model and the proposed license model are applicable for the various types of fair use for user and those models enable providers to develop new business models.

Superdistribution is required in many DRM systems that require rapid and smooth distribution. However, current superdistribution mechanisms do not appear to support certain user needs for contents use. In this paper, we enhance superdistribution to endow it with contents flexibly, and propose a license distribution mechanism to distribute contents securely in the superdistribution. The contents encryption key is encrypted using device identifier of consumer who is superdistributed lastly. The encrypted key is connected to some accumulated device identifiers of consumers. These perform superdistribution in the proposed method. In evaluation, we compared the proposed method with that of the existing DRM systems, and believe to have demonstrated that the proposed method results in increase flexibility for contents use.