Abstract
COVID-19 has been endangering people's lives and causing a huge burden on the healthcare sector. To limit the fast spread of the virus, contact tracing systems are currently adopted worldwide to identify the close contacts of positive cases during the incubation period of the virus and notify them to quarantine. However, the existing systems are vulnerable to security and privacy attacks and suffer from large communication and computation overheads. To address these limitations, in this paper, we propose an efficient and privacy-preserving contact tracing system based on a consortium Blockchain. Instead of depending on one entity to run the system, our system is run in a decentralized fashion by multiple health authorities that construct the Blockchain network. The utilization of Blockchain secures our system against the problems of centralized architecture. Besides, our system is designed to thwart the false reporting (panic) attack, while preserving the privacy of the users against identification and social graph disclosure attacks. The performance evaluation of our system demonstrates its efficiency in terms of communication and computation.