CITADEL: a content protection architecture for decentralized peer-to-peer file sharing systems

There is an increased interest, by content creators and owners, in content protection systems that provide the ability to control or restrict the content that can be shared on peer-to-peer file sharing systems. Some content protection systems have been proposed for centralized peer-to-peer systems (such as Napster) where a central authority controls all indexing and querying. These systems cannot be applied to decentralized peer-to-peer systems since they rely on a central server. Also, such systems limit the ability of end-users to effectively share content and can make the peer-topeer distribution model resemble a client-server model in many respects. In this paper, we propose CITADEL, a novel content protection architecture designed to operate in decentralized peer-to-peer systems (such as Gnutella). CITADEL enforces a range of protection policies while maintaining an open peer-to-peer distribution model. CITADEL builds a protected file sharing environment over a normal peer-to-peer network using secured content objects and file sharing software enhanced to perform protection operations. A flexible content importation system that is part of CITADEL allows all users to insert new content as well as additional copies of protected content.