FMSM: A Fuzzy Multi-keyword Search Scheme for Encrypted Cloud Data based on Multi-chain Network

Searchable encryption is an efficient and secure solution that can perform search operation in ciphertext on cloud servers. It is widely used by a growing number of businesses and individuals. However, most existing searchable encryption schemes typically overestimate the security level of the cloud server, which is an untrusted and centralized third party in fact. The emergence of blockchain technology solves the trustworthiness problem of the third party with features such as decentralization, verifiability and immutability. The combination of searchable encryption and blockchain technology uses the smart contract instead of the cloud server to execute ciphertext search task, which improves security and efficiency of search significantly. We propose a Fuzzy Multi-keyword Search Scheme for Encrypted Cloud Data based on Multi-chain Network (FMSM). FMSM is a distributed searchable encryption scheme since we adopt a multi-chain architecture. It not only supports fuzzy multi-keyword search and dynamic updates for encrypted cloud data, but also supports parallel processing of data. In FMSM, counting bloom filter and MinHash algorithm are used to construct index vectors and query vectors on the corresponding two chains, besides, the search is done on a third chain. All of these calculation tasks are executed in the way of distributed computing, which makes the index construction and search process more efficient and the sorting results more accurate. The security analysis and performance evaluation show that the FMSM has high security, reliability, search efficiency and accuracy.