Quantum secure privacy preserving technique to obtain the intersection of two datasets for contact tracing

Contact tracing has emerged as a powerful and effective measure to curb the spread of contagious diseases. It is a robust tool, but on the downside, it possesses a risk of privacy violations as contact tracing requires gathering a lot of personal information. So there is a need for a cryptographic primitive that obfuscate the personal data of the user. Taking everything into account, private set intersection seems to be the natural choice to address the problem. Nearly all of the existing PSI protocols are relying on the number theoretic assumption based hard problems. However, these problems are not secure in quantum domain. As a consequence, it becomes essential to designing PSI that can resist quantum attack and provide long-term security. One may apply quantum cryptography to develop such PSI protocol. This paper deals with the design of PSI using quantum cryptography (QC), where the security depends on the principles of basic quantum mechanics. Our scheme achieves long-term security and remains secure against quantum attacks due to the use of QC. As opposed to the existing quantum PSI protocols, the communication and computation costs of our scheme are independent of the size of universal set. Particularly, our proposed protocol attains optimal communication cost in the context of quantum PSI. In addition, our designed protocol needs smaller amount of measurements. Moreover, we require only single photon quantum resources and simple single-particle projective measurements, unlike most of the existing quantum PSI protocols.