FASE: A Fast and Accurate Privacy-Preserving Multi-Keyword Top-k Retrieval Scheme Over Encrypted Cloud Data

With the advance of cloud computing technology, increasingly more documents are encrypted before being outsourced to the cloud for great convenience and economic savings. In this paper, we propose a fast and accurate searchable encryption (FASE) scheme that supports accurate top-k multi-keyword retrieval. We utilize a homomorphic orderpreserving encryption algorithm to encrypt the index and query vectors. The encryption method can not only ensure that the calculation of relevance score (SIi * T) is not exposed to the cloud server, but also protect the privacy of ranking operator. Compared to the traditional method, there are no dummy keywords added to the query vector and document vector, and the top-k search precision of the FASE scheme is 100%. To improve the search efficiency, a large number of irrelevant documents are effectively filtered by matching the document mark vector and query mark vector. Furthermore, according to the two-round ranking of the keyword matching degree and the relevance score, not only more accurate search result is returned, but the search efficiency is also further improved. The theoretical analysis and experimental results show that the FASE scheme can achieve fast and accurate multi-keyword ranking search.