Private Key Management in Hierarchical Identity-Based Encryption

Hierarchical Identity-Based Encryption (HIBE) is a generalization of IBE that mirrors an organizational hierarchy, which consists of a root private key generator (PKG), domain PKGs and users. In a traditional HIBE system, users retrieve private keys from their domain PKGs, while domain PKGs request domain secret keys from the root PKG. What's more, the manager of each private key is a single one. Unfortunately, some of the PKGs(private key manager) could be untrusty, such that they would leak lower level's private keys. In this paper, we propose a novel private key management scheme in HIBE, where a domain master key is not charged by a single one, but a group PKGs aiming at avoiding unreliable PKGs' attack.