Decentralized Multiauthority Attribute-Based Searchable Encryption for E-Health Cloud

Electronic medical records (EMRs) are the essential sensitive personal data that is shared between patients and doctors through the semi-trusted E-health cloud. In the real application, multiauthority ciphertext-policy attribute-based searchable encryption (MA-CP-ABSE) is suitable to protect the security of the EMR for it possesses fine-grained access permission, efficient key management, and retrieval function over the encrypted data. However, previously proposed MA-CP-ABSE schemes are commonly restricted by the central authority, which is required by all attribute authorities in some operations like generating users’ secret keys. To deal with this issue, we proposed a decentralized MA-CP-ABSE (DMA-CP-ABSE) scheme. In our scheme, any attribute authority can become an independent authority to generate a secret key, which is no longer controlled by the central authority. Furthermore, a single-keyword search will produce many disrelated search results. For this, we enhance the DMA-CP-ABMSE scheme by implementing a multikeyword search function to improve the search accuracy. Besides, to handle the dynamic changing of access permission, we have designed the attribute revocation methods. Finally, we process the formal security analysis to demonstrate our scheme is secure under the chosen-keyword attack (CKA) and implement experiments to show its efficiency and feasibility.