COVERT-Blockchain: Privacy-Aware Contact Tracing for COVID-19 on a Distributed Ledger

Privacy preservation in contact tracing for COVID-19 is challenging as such applications tend to reveal users sensitive data which is shared together with their location. This paper proposes COVERT-Blockchain, a novel distributed ledger based platform for contact tracing without revealing users privacy where infected users only share their anonymized location traces on the Blockchain with a sliding window. To further reduce the chances of revealing the corresponding users' trajectories, in COVERT-Blockchain we employ an adaptive logging mechanism to store trajectory data for contact tracing only if the users stayed in a location for longer time duration. COVERT-Blockchain is evaluated for scalability and robustness in terms of overhead and delays in storing and retrieving data, results show it to be efficiently achieving contact tracing without privacy leakage.