A Blockchain Based Framework for Complete Secure Data Outsourcing with Malicious Behavior Prevention

Outsourcing information on the cloud server is a method to reduce the computational and storage overhead resulted from data owners' huge amount of information. Considering the fact that this information could be sensitive, encryption is used before outsourcing. But this prevents efficient searching. Searchable encryption is an approach that provides security alongside efficiency. So far, many searchable encryption schemes have been presented in which the server is modeled as an honest but curious entity. But in case the server is malicious, the accuracy of the information will be at stake. For this purpose, we propose a multi-server searchable symmetric encryption scheme without the need to trust the cloud servers, using blockchain and smart contract, which works efficiently in addition to ensuring the accuracy of information. Moreover, this scheme involves a fair mechanism to preserve the interests of users and servers and prevent their malicious actions.