A cross-blockchain based distributed crowdsouring system for Internet of Things

With the development of Internet of Things (IoT) technologies, the mobile crowdsourcing has become the most effective and reliable method for data collection and processing. However, as huge amounts of data are generated in mobile crowdsourcing services, data privacy and security has become a key challenge for IoT. To address this challenge, a Cross-Blockchain based Distributed mobile Crowdsourcing System, named CBDCS, is proposed in this paper. In CBDCS, to overcome the privacy leakage problem caused by a single-point failure, the blockchain is used as a crowdsourcing task server, based on which an improved multi-subchain structure is designed. Then, based on multi-subchain, a task hierarchical storage mechanism is proposed, which stores different levels of tasks in corresponding subchains to improve privacy protection. In addition, CBDCS meet the demands of workers for tasks through a cross-subchain mechanism based on root&sub CA and smart contracts, while guaranteeing data privacy. Extensive simulation results demonstrate that the CBDCS can obtain high throughput, low overhead, and data privacy under various IoT scenarios.