International Association
for Cryptologic Research

This paper studies a multi-party private set union (mPSU), a fundamental cryptographic problem that allows multiple parties to compute the union of their respective datasets without revealing any additional information. We propose an efficient mPSU protocol which is secure in the presence of any number of colluding semi-honest participants. Our protocol avoids computationally expensive homomorphic operations or generic multi-party computation, thus providing an efficient solution for mPSU.

The crux of our protocol lies in the utilization of new cryptographic tools, namely, Membership Oblivious Transfer (mOT) and Conditional Oblivious Pseudorandom Function (cOPRF). We believe that the mOT and cOPRF may be of independent interest.

We implement our mPSU protocol and evaluate their performance. Our protocol shows an improvement of up to $55\times$ and $776.18\times$ bandwidth cost compared to the existing state-of-the-art protocols.