CRYPTO '93 Proceedings of the 13th annual international cryptology conference on Advances in cryptology
Collusion-Secure Fingerprinting for Digital Data (Extended Abstract)
CRYPTO '95 Proceedings of the 15th Annual International Cryptology Conference on Advances in Cryptology
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CSS, the first system to protect multimedia content on the new DVD medium failed badly, because both its encryption algorithm and its key management could easily be broken. A new industry initiative, the 4C Entity, LLC (founded by IBM, Intel, Matsushita and Toshiba), presents a more mature approach, called "Copy Protection for Prerecorded Media" (CPPM), which has already been adopted in DVD-Audio.A key-feature of CPPM is its advanced key-management, which allows for system renewability by revoking compromised devices. Renewability means that content provider can encrypt the content, such that compromised devices cannot decrypt it, whereas non-compromised devices still can.In this paper, we review the basic concepts of CPPM and propose a framework to study its cryptographic strengths based on the published specifications. We will focus our assessment especially on CPPM's key-management scheme, which, unfortunately, is not completely specified in the official publicly available specification. As a consequence, it is currently unknown, how the 4C Entity selects the device keys that are assigned to devices. As a main contribution we propose several suitable key-assignment strategies based on finite geometric structures and study their security.