A blockchain-based multi-keyword rank search scheme for B+ tree inverted index

In the cloud storage environment, data providers encrypt their data before transferring it to the cloud server to reduce storage pressure and facilitate internal sharing. However, most of the plans have certain drawbacks, such as: the search efficiency is low, the cloud server central problem is serious, and the ability to resist keyword guess attack is poor et al. To overcome these shortcomings, this paper presents a blockchain-based multi-keyword rank search scheme for B+ tree inverted index to improve the search accuracy and efficiency. First, we choose the top-$k$ keywords with high weight to build a B+ tree inverted index. Then, the cloud server calculates the relevance score of ciphertext using the optimized TF-IDF formula and sends the top-$k$ ciphertexts to the user. In addition, verification and match contract on the blockchain to verify the identity of users and address the semi-trust and centralization of cloud server. We have deployed reward and punishment contracts on the blockchain to regulate the behavior of data providers and cloud server. Rigorous security certification shows that the scheme can resist choose keyword attack (CKA) and keyword guess attack (KGA). Through experiments, it is found that our scheme has good search efficiency and communication efficiency.