Hierarchical attribute based encryption with continuous leakage-resilience.

Attribute based encryption (ABE) is widely applied in cloud computing settings due to its fine-grained access control. Most ABE schemes do not consider the side channel attacks which may leak the secret information of cryptosystems. Leakage-resilient cryptography aims to model security for various side channel attacks. In this paper, we first give the formal definition and security model of hierarchical attribute based encryption (HABE) with continuous leakage-resilience. Furthermore, we present a ciphertext-policy HABE scheme with continuous leakage-resilience. The proposed scheme is resilient to master key leakage and secret key leakage. We prove the security of our scheme under composite order bilinear group assumptions by using dual system encryption techniques. The performance of leakage-resilience is analyzed theoretically. If the depth of our proposed scheme is 1, the relative leakage ratio is almost up to 1/3. In addition, we give the performance comparison through experiments.