Comments on “BSIF: Blockchain-Based Secure, Interactive, and Fair Mobile Crowdsensing”

Mobile crowdsensing (MCS) is a promising sensing paradigm which allows users to outsource a range of sensing tasks to a crowd of mobile workers with mobile devices. Location-dependent MCS, as the name implies, is a geographically-dependent sensing paradigm in which service requestors outsource location-specific tasks to many workers with mobile devices, and the workers accepting the tasks collect data at a particular location by physically arriving at the desired locations. Many efforts have been devoted to protecting location privacy of the workers accepting the tasks while ensuring task allocation accuracy and efficiency. In 2022, Wang et al. proposed BSIF, a blockchain-based MCS system (published in IEEE Journal on Selected Areas in Communications (JSAC)) that can prevent not only illegitimate participants but also location privacy leakage. For the purpose of protecting location privacy, they proposed a location-based symmetric key generation algorithm, which coordinates session keys for the target ranges between the service requestor and the workers accepting the tasks without revealing the location information. However, in this paper, we will point out a flaw in their location-based symmetric key generation algorithm, which indicates that BSIF does not work. Furthermore, we propose a novel approach to achieve the location-based symmetric key generation using a witness encryption scheme.