Managing encryption and key publication independently in digital rights management systems
Secure distribution of digital goods is now a significantly important issue for protecting publishers' copyrights. In this paper, we study a useful primitive for constructing a secure and efficient digital rights management system (DRM) where a server which encrypts digital content and one which issues the corresponding decryption key works independently, and existing schemes lack this property. We first argue the desired property necessary of an encryption scheme for constructing an efficient DRM, and formally define an encryption scheme as split encryption scheme containing such property. Also, we show that an efficient split encryption scheme can be constructed from any identity-based scheme. More precisely, we show an equivalence result implying that a split encryption scheme for some system parameter setting and an identity-based encryption scheme have the same primitives but for different uses. Since currently there is no identity-based encryption scheme which is based on well-known computational assumption and/or provably secure in the standard model (i.e. without the random oracle model), by reasonably tuning the system parameter, we show another construction of split encryption which is secure against chosen ciphertext attacks in the standard model assuming that decision Diffie-Hellman problem is hard to solve.
digital rights management systems copyright protection semantic security adaptive attacks