Privacy-Preserving Spatial Crowdsourcing Based on Anonymous Credentials

In Spatial Crowdsourcing (SC), a set of spatio-temporal tasks are outsourced to a set of workers, i.e., individuals with mobile devices who physically travel to task locations. The process of matching workers to tasks is performed by a SC server. To perform matching, the SC server needs access to worker locations. However, the SC server may not be trustworthy. Current solutions for protecting locations of workers assume that a trusted cellular service provider (CSP) knows the identities and locations of workers and sanitizes locations before sharing them with the SC server. In practice, the CSP may not have the technical ability, nor the proper incentives to perform the sanitization task. Thus, location protection must be performed by a Location Privacy Provider (LPP). To prevent identity disclosure to the LPP, we propose a novel solution based on anonymous credentials which preserves worker privacy. Our solution allows registered workers to log on to the LPP and receive tasks from the SC-server anonymously. In addition, our solution assures the confidentiality and integrity of spatial tasks. Our implementation and experiments demonstrate that our solution is practical.