Blockchain-assisted multi-keyword fuzzy search encryption for secure data sharing

Cloud-based data sharing has become a significant technology trend thanks for its convenience and economy. Data owners are suggested to encrypt data before outsourcing for data security and users’ privacy. This approach makes it a challenging problem to implement the retrieval of encrypted data while enforcing fine-grained access control over the ciphertext. In this paper, we propose a blockchain-assisted multi-keyword fuzzy search encryption (BCFSE) scheme for secure data sharing which supports fine-grained access control and attribute revocation. The BCFSE scheme maps the attributes in the ciphertext policy attribute-based encryption (CP-ABE) to attribute tokens on the blockchain, which provides lightweight, secure and trusted attribute management. Moreover, we construct a keyword search scheme based on CP-ABE by using searchable symmetric encryption algorithm in the keyword encryption and retrieval phases, effectively reducing computational cost. BCFSE combines the advantages of CP-ABE and searchable encryption based on blockchain, which implements authorization and search with the assistance of smart contracts to ensure the reliability of the search process. In addition, the BCFSE scheme supports multi-keyword fuzzy search with both AND and OR semantics. Extensive experiments have been performed on real datasets to validate the effectiveness and efficiency of our BCFSE scheme.