Efficient and Provable Secure Anonymous Hierarchical Identity-based Broadcast Encryption (HIBBE) Scheme without Random Oracle

Hierarchical identity-based broadcast encryption (HIBBE) organizes the users in a tree-like structure in which they can delegate the decryption ability to their subordinates. In addition, the trusted third party (TTP) can reduce its burden because the users’ secret keys can be generated in a distributed mechanism by users’ supervisors. HIBBE enables encrypting a message for any arbitrary set of receivers, and only the chosen users and their supervisors are able to decrypt. To preserving the anonymity of the intended receivers, in this paper, for the first time, we propose an anonymous HIBBE scheme. The proposed scheme is constructed based on composite order bilinear maps. We formally define the anonymity against chosen identity vector set and chosen plaintext a‚ack (Anon-CIVS-CPA), and prove that the proposed scheme provides this property. Performance evaluation shows the practical and deployable aspects of our proposed scheme. With the advantage of HIBBE, we enable hierarchical identity-based signature (HIBS) schemes to sign a message for a set of designated verifiers. This resulted in proposing a generic construction for the novel notion of hierarchical identity-based multi-designated verifiable signature (HIB-MDVS). We formally define HIB-MDVS’s security against existential forgery under chosen message a‚ack (EF-CMA), prove that the resulting HIB-MDVS is unforgeable, and finally show that it provides the anonymity of the intended verifiers.