Multi-authority attribute-based encryption access control scheme with hidden policy and constant length ciphertext for cloud storage

In order to protect user privacy, save storage overhead and implement flexible and fine-grained access control, a multi-authority CP-ABE access control scheme with hidden policy and constant length ciphertext is proposed, and the scheme proves to be CPA-secure under the security model. The user's private key is generated by multiple authorities to alleviate damage of broken authorities to the system. The central authority publishes public parameters, and generates signature tags for users and authorities. However, it does not participate in the generation of any master key or attribute private key, thus avoiding the key escrow problem. The access structure is hidden within the ciphertext, so that malicious users are unable to obtain sensitive information through the access structure, which effectively protects user privacy. In addition, this scheme realizes constant length ciphertext. The number of exponentiation operation for encryption and bilinear pairing operation for decryption are fixed. Finally, theoretical analysis and experimental results show that the performance of our scheme is significantly superior to that of comparable schemes.