Blockchain-assisted multi-keyword searchable provable data possession for cloud storage

Keyword searchable provable data possession (PDP) is a type of schemes that aim to achieve a higher level capability in auditing, as most existing PDP schemes fail in having satisfied ability in auditing integrity of data containing the same types of properties. However, these schemes encounter a few challenges. One challenge is that files that users need to auditing will be lost since using single keywords may fail in achieving an accurate search. The other challenge is the integrity of the outsourced data is threatened by those attacks targeting at the Cloud Server (CS) side, such as the integrity loss of search results, pre-matching attacks, and pre-computation attacks. In this paper, we propose a scheme entitled multi-keyword searchable PDP (MKPDP) that aims to improve the accuracy of searchable files auditing and guarantee the integrity of data containing a specific kind of properties that participate in the auditing process. Specifically, we have developed an index matrix combining with a tag index to achieve multi-keyword files searchability. A blockchain-based data storage is constructed to store index information, which ensures the integrity of the searching files and prevents CS from using incomplete searching results to generate proof information. Our security analysis and evaluations have demonstrated that the proposed MKPDP is provably secure and efficient.