An Outsourced Multi-authority Attribute-Based Encryption for Privacy Protection with Dynamicity and Audit

Attribute-based Encryption (ABE) realizes a novel and practical many-to-many encryption paradigm, in which the encryptor can appoint someone to decrypt it, and the decryptor does not know who the encryptor is. Therefore, the ABE has better privacy preserving to a certain extent for both participants to a certain degree. The original attribute-based encryption scheme usually has only one trusted authority, and the state of the system is not flexible enough to meet various dynamic needs of users, which become the bottleneck of the system. In addition, the computational overhead of the decryption is not cheap. In order to reduce the cost of decryption, a series of schemes such as encryption/decryption outsourcing have been proposed. However, those solutions simply outsource the process independently without any in-depth investigation into the trustworthiness issues. Hence, we construct an outsourced multi-authority attribute-based encryption with dynamicity and auditing (OMADA-ABE), which makes the system more practical and more flexible. Our solution can support the dynamic changes of the system as well as the auditing of outsourced decryption information to solve the above-mentioned related problems, so as to meet the potential requirements related to the real-world system. What’s more, we prove that the proposed scheme is secure against selective chosen-ciphertext attacks without random oracles, and it also achieves the collusion resistance. Finally, we compare our scheme with related researches and showed our advantage regarding the performance and other aspects.