Contact Tracing with Location Privacy Protection

The COVID-19 pandemic has highlighted how important contact tracing is for quickly identifying new infections and slowing the spread of disease. Contact tracing focuses on finding people who have been in close contact with confirmed cases, which can also help uncover infections that might otherwise go unreported. When building contact tracing systems, it’s crucial to protect people’s privacy and keep mobile device power usage low - both of which are key to gaining public trust and encouraging widespread adoption. In this paper, we introduce three contact tracing protocols - basic, improved, and advanced - based on homomorphic encryption, where multiple servers work together to perform tracing. The basic and improved protocols protect users’ location privacy, while the advanced protocol goes further by also safeguarding quarantine privacy, as long as at least one server remains honest. Experimental results show that the basic protocol is the most efficient, while the improved and advanced versions are practical and feasible to deploy.