Private set intersection (PSI) is a powerful cryptographic technique that allows two parties to compute the intersection of their data without exposing their raw data to the other party. In other words, PSI allows to test whether the parties share a common datapoint (such as a location, ID, etc). More precisely, it is a technique that enables two parties, which both have a set of data points, to compare these data sets without giving up on their individual data privacy. It is a privacy-preserving technique that allows for two parties to compute the intersection of their data. The result is a third data set with only those elements, which both parties have in common. PSI is useful for the following case: Private Contact Discovery, DNA testing and pattern matching, Remote diagnostics. In this current scenario, PSI is very useful technique to trace covid patients.