The paper “Pool: A Practical OT-based OPRF from Learning with Rounding”, co-authored by LASIGE’s integrated researcher Alex Davidson, was accepted to be presented at ACM CCS 2025, a CORE A* conference. The work was performed in collaboration with researchers Amit Deo (Zama) and Louis Tremblay Thibault (Zama, ÉTS Montréal).

This research explores new constructions of Oblivious Pseudorandom Function (OPRF) protocols that are secure against adversaries with quantum computing resources. OPRFs are fundamental cryptographic protocols, that have applications in developing privacy-preserving interactions on the Internet, and are already standardised by the Internet Engineering Task Force (RFC9497). This work produces a new construction, named Pool, with security based on the binary learning with rounding problem. The advantages of Pool, when compared with prior work, are that it is quantum-safe, reliant on a well-known cryptographic hardness assumption, and that it is more efficient than previous schemes that have not been weakened by active cryptanalysis. Pool provides security against semi-honest adversaries, and thus is a candidate proposal for building post-quantum variants of private set intersection protocols, amongst other real-world information sharing applications. Valuable future work would investigate whether the design philosophy behind Pool could be used to construct more efficient instantiations of OPRF protocols, that maintain security against generic malicious adversaries.

ACM CCS 2025 will take place at Taipé, Taiwan, from October 13  to 17, 2025.