Efficient privacy-preserving decentralized ABE supporting expressive access structures

Decentralized multi-authority attribute-based encryption (ABE) has been adopted to protect outsourced data. However, there are some security issues. Firstly, the user's attributes information is leaked to the authorities and secondly, the access structure being sent along with ciphertext violates its privacy. To address these issues, an efficient decentralized attribute-based encryption scheme with features of privacy preservation and expressive access structures is proposed. The proposed scheme cannot only prevent user's attributes information leakage, but it also provides a hidden, flexible and expressive structure realizable by Linear Secret Sharing Scheme (LSSS). Moreover, we prove the proposed scheme to be secure against Chosen-Ciphertexts Attacks (CCA) under the standard Decisional Bilinear Diffie-Hellman (DBDH) assumption. In addition, proposed scheme performs efficiently in comparison to existing schemes shown by theoretical and experimental analysis.