  The popularity and applicability of mobile crowdsensing applications are
continuously increasing due to the widespread of mobile devices and their
sensing and processing capabilities. However, we need to offer appropriate
incentives to the mobile users who contribute their resources and preserve
their privacy. Blockchain technologies enable semi-anonymous multi-party
interactions and can be utilized in crowdsensing applications to maintain the
privacy of the mobile users while ensuring first-rate crowdsensed data. In this
work, we propose to use blockchain technologies and smart contracts to
orchestrate the interactions between mobile crowdsensing providers and mobile
users for the case of spatial crowdsensing, where mobile users need to be at
specific locations to perform the tasks. Smart contracts, by operating as
processes that are executed on the blockchain, are used to preserve users'
privacy and make payments. Furthermore, for the assignment of the crowdsensing
tasks to the mobile users, we design a truthful, cost-optimal auction that
minimizes the payments from the crowdsensing providers to the mobile users.
Extensive experimental results show that the proposed privacy preserving
auction outperforms state-of-the-art proposals regarding cost by ten times for
high numbers of mobile users and tasks.
