Existing data sharing schemes mainly use attribute-based encryption technology to achieve "one-to-many" data access control, but there are problems such as low encryption efficiency and attributes that are easily tampered with. To solve these problems, a blockchain-based ciphertext data sharing scheme is proposed. Combining attribute-based encryption and symmetric encryption algorithms, confidentiality and fine-grained access control of shared data are achieved. The introduction of an on-line/off-line encryption mode greatly improves the encryption performance of the data owner. In addition, it uses outsourcing computing technology to reduce the computing burden of data access users. Attribute sets and Hash values of shared data are uploaded to the blockchain. This ensures the ‘unforgeability’ of attributes and the correctness of decrypted ciphertext. The analysis shows that this scheme realizes secure data sharing, and its encryption/ decryption efficiency is better than similar schemes. Hence, it is more suitable for resource-constrained smart devices.