Fast Enhanced Private Set Union in the Balanced and Unbalanced Scenarios

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Presented at USENIX Security 2025 by

Private set union (PSU) allows two parties to compute the union of their sets without revealing anything else. It can be categorized into balanced and unbalanced scenarios depending on the size of the set on both sides. Recently, Jia et al. (USENIX Security 2024) highlight that existing scalable PSU solutions suffer from during-execution leakage and propose a PSU with enhanced security for the balanced setting. However, their protocol's complexity is superlinear with the size of the set. Thus, the problem of constructing a linear enhanced PSU remains open, and no unbalanced enhanced PSU exists. In this work, we address these two open problems: