A Tree-based CP-ABE Scheme with Hidden Policy Supporting Secure Data Sharing in Cloud Computing

With flexible and scalable features for fine-grained access control, Ciphertext Policy Attribute-based Encryption (CP-ABE) is widely used as a kind of data protection mechanism in the cloud computing. However, the access policy of CP-ABE scheme may contain sensitive information which causes privacy revelation of the data provider or receiver. Some papers proposed hidden policy CP-ABE scheme, which are based on And-gate access structure whose expressive ability of access policy is limited. CPABE with the tree-based access structure has stronger expressive ability and more flexible access control capability. Therefore, it has broad application prospects compared to other mechanisms. This paper proposes a tree-based access structure CP-ABE scheme with hidden policy (CP-ABE-HP), which can both protect the policy and has flexible access control capability. We prove the Chosen-plaintext Attack (CPA) security of our scheme under the Decisional Bilinear Diffie-Hellman (DBDH) assumption in the standard model.