Research On Attribute-based Broadcast Encryption Scheme

Broadcast encryption provides a way to distribute confidential message at the same time to users who listen to the broadcast channel. As an important part of information security, broadcast encryption has become the research focus in recent years. Compared with traditional broadcast encryption scheme, attribute-based broadcast encryption receives more attention because of its flexible access control policy.On the basis of in-depth study of the related work, this thesis proposes two efficient attributebased broadcast encryption schemes. A user could decrypt the ciphertext by bilinear pairing operations only if his identity information is included in the broadcast set and his attributes satisfy the access policy. Given the linear relationship among ciphertext length, encryption/ decryption costs with the attribute numbers in the existing attribute-based broadcast encryption schemes, the first scheme is proposed. Based on elliptic curve encryption algorithm, our scheme uses dynamic threshold access structure, and the threshold value can be adjusted dynamically according to the need of the encrypting party. In the scheme, the ciphertext size and the bilinear pairing operation times in encryption and decryption are constant, which can reduce the overhead of broadcast communication and ensure a high efficiency. Security analysis and performance analysis are provided in the thesis, meanwhile the experiment simulation is carried out and simulation results verify the validity of the scheme. Then, this thesis presents a fully secure and constant-size ciphertext attribute-based broadcast encryption scheme through the dual system encryption technology. Dependent on three static assumptions, the scheme can prove to be fully secure under the standard model. The security proof is provided in the thesis, both performance analysis and the experiment simulation are carried out, simulation results verify the validity of the scheme.