Blockchain-Assisted Attribute-Based Ciphertext Ranked Search Scheme

With the advent of cloud computing and cloud storage, more people are uploading local data encryption to cloud server to save storage space. Searchable encryption techniques can search encrypted data without decrypting the data. Currently, attribute-based searchable encryption schemes are widely studied because they are more in line with practical needs, but most attribute-based searchable encryption schemes do not support ranked of search results and do not consider attribute revocation. In addition, cloud server are semi-trustworthy and may return incorrect results due to savings in computational overhead, and data users need to verify search results locally. To address the above issues, this paper proposes a blockchain-assisted attribute-based ciphertext ranked search scheme with revocation function. It combines searchable encryption with blockchain and uses smart contracts to verify the correctness of the results returned by the cloud server without local verification by users. The ciphertext are ranked using Term Frequency-Inverse Document Frequency (TF-IDF) technology. The security analysis shows that the scheme achieves the indistinguishability of keyword ciphertext and the indistinguishability of trapdoor, and the experimental analysis proves the effectiveness of the scheme.