Quantum Secure Disease Surveillance Through Private Set Intersection

The healthcare pandemic (for instance, the recently ongoing Coronavirus disease (COVID-19) pandemic) presented a challenge for researchers to find novel techniques to limit the transmission of the virus. In this context, contact tracing has emerged as an important method to curb the spread of disease. Although it can help combat disease outbreaks, if the contact tracing is executed without careful consideration then it could jeopardize the users’ privacy. The cryptographic technique, private set intersection (PSI) appears to be a logical solution. However, many existing PSI protocols rely on the security of number theory based problems, which are vulnerable in the quantum domain. Therefore, to address this issue we present a PSI protocol (namely qPSI) based on quantum cryptography. The communication and computational costs of existing schemes depend on the universal set size N. In comparison, qPSI requires computational and communication costs, which are independent of the universal set size N. Moreover, the existing Bloom filter based quantum PSI does not provide the exact intersection due to high false positive rate of the Bloom filter of server’s private set, whereas qPSI is not affected by the false positive rate and provides the exact set intersection. In addition, quantum PSI protocols use multi-particle entangled state or N single photons, and complicated oracle operators in N-dimensional Hilbert space. On the other hand, qPSI only utilizes single-photon quantum resources and projective measurements operations over a 2-dimensional Hilbert space. Therefore, qPSI is simple and efficient when compared to other existing PSI protocols in the state-of-the-art.