We present a solution to the problem of privacy invasion in a multiparty digital rights management scheme. (Roaming) users buy content licenses from a content provider and execute it at any nearby content distributor. Our approach, which does not need any trusted third party--in contrast to most related work on privacy-preserving DRM--is based on a re-encryption scheme that runs on any mobile Android device. Only a minor security-critical part needs to be performed on the device's smartcard which could, for instance, be a SIM card.
@cite_4 present a privacy-preserving DRM scheme for two- and multiparty scenarios without needing a TTP. A user anonymously requests a token set from the content owner that allows anonymous purchase of content licenses from content providers. A drawback is that content providers are able to build usage profiles of content executions under a pseudonym. @cite_5 present a DRM scenario that allows users to anonymously buy software from any software provider and execute it at any computing center within the cloud. The users' permission to execute the software is checked before every single execution. Their solution is resistant against profile building. The authors suggest employing a software re-encryption scheme that is based on secret sharing and homomorphic encryption to achieve unlinkability of software executions towards the computing center. Their software re-encryption scheme is rather complex and implies a huge communication overhead. The approach is extended in @cite_18 by employing an adapted version of proxy re-encryption @cite_14 . The scheme makes explicit use of a service provider as a TTP.
@cite_5 @cite_18 @cite_14 @cite_4
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We come up with a digital rights management (DRM) concept for cloud computing and show how license management for software within the cloud can be achieved in a privacy-friendly manner. In our scenario, users who buy software from software providers stay anonymous. At the same time, our approach guarantees that software licenses are bound to users and their validity is checked before execution. We employ a software re-encryption scheme so that computing centers which execute users' software are not able to build user profiles -- not even under pseudonym -- of their users. We combine secret sharing and homomorphic encryption. We make sure that malicious users are unable to relay software to others. DRM constitutes an incentive for software providers to take partin a future cloud computing scenario. We make this scenario more attractive for users by preserving their privacy. In 1998, Blaze, Bleumer, and Strauss (BBS) proposed an application called atomic proxy re-encryption, in which a semitrusted proxy converts a ciphertext for Alice into a ciphertext for Bob without seeing the underlying plaintext. We predict that fast and secure re-encryption will become increasingly popular as a method for managing encrypted file systems. Although efficiently computable, the wide-spread adoption of BBS re-encryption has been hindered by considerable security risks. Following recent work of Dodis and Ivan, we present new re-encryption schemes that realize a stronger notion of security and demonstrate the usefulness of proxy re-encryption as a method of adding access control to a secure file system. Performance measurements of our experimental file system demonstrate that proxy re-encryption can work effectively in practice. A content distribution mechanism for DRM needs to satisfy the security and accountability requirements while respecting the privacy of the parties involved. However, achieving privacy along with accountability in the same framework is not easy as the requirement for achieving these attributes are conflicting each other. Most of the current content distribution mechanisms rely on trusted third parties to achieve privacy along with these attributes. In this paper, we propose a privacy preserving content distribution mechanism without requiring trust over any third party by using the mechanisms of blind decryption and one way hash chain. We prove that our scheme is not prone to the ‘oracle problem’ of the blind decryption mechanism. Our mechanism supports revocation of even malicious users without violating their privacy.