On privacy enhancement using u-indistinguishability to COVID-19 contact tracing approach in Korea

South Korea's COVID-19 contact tracing is unique because detailed and personally sensitive information has been disclosed. As a result, privacy concerns and controversies have been raised. As long as the Korean format of contact information is to be shared, a more sophisticated technique is required to mitigate the risk of privacy breaches. To meet the requirement of minimum privacy infringement, technical solutions for privacy enhancement are needed. In this paper, a u-indistinguishability concept is proposed and its effectiveness is shown. By mixing at least u patients' quasi-identifiers into a cluster and their associated movement information into another cluster, linkability is weakened significantly.