T-HIBE: A Trustworthy HIBE Scheme for the OSN Privacy Protection

The Hierarchical Identity-Based Encryption (HIBE) scheme can efficiently provide confidential communication and privacy protection to online social networks. However, the inherent key escrow problem and the secure key distributing problem primarily hinder the widespread adoption of the cryptographic scheme in practice. To address the key escrow problem, this paper introduces a provably secure escrow-free model, which employs multiple Key Privacy Authorities (KPAs) to restrict the power of Public Key Generators (PKGs) in HIBE scheme. To achieve the goal of secure key distributing, this paper proposes an efficient mechanism which imposes user calculated blinding factors when distributing private keys. We instantiate the proposed model into an trustworthy and secure HIBE scheme called T-HIBE scheme, and prove that the scheme is IND-ID-CCA secure under standard model.