Hierarchical authority key-policy attribute-based encryption

Based on the key-policy attribute-based encryption (KP-ABE), combined with the idea of hierarchical ID-Based encryption (HIBE), a hierarchical authority key-policy attribute-based encryption (HA-KP-ABE) scheme is presented. The new scheme uses hierarchical multi-authority to distribute private keys to users. It can not only relieve the burden with a single authority but also avoid the potential safety hazard when the central authority (CA) is untrusted or attacked. Moreover, private keys are computed for users according to random polynomials, different users can not collude. Access tree is used in the phase of key generation and different users´ attribute sets are allowed to overlap, achieving fine-grained access control. Its security can be reduced to the decisional modified bilinear Diffie-Hellman (MBDH) assumption.