Threshold Oblivious Pseudorandom Functions from Isogeny Group Actions

Robi Pedersen

Paper 2026/489

Threshold Oblivious Pseudorandom Functions from Isogeny Group Actions

Robi Pedersen

, Technical University of Denmark

Abstract

We present a new verifiable oblivious pseudorandom function (VOPRF) from isogeny group actions. Our construction is twice as fast as the previous state of the art of Delpech de Saint Guilhem and Pedersen at a slightly higher communication cost. One major contribution is the realization of a new proof protocol that is integrated as a two-party computation into the OPRF protocol, making the output verifiable. The main design choice behind our construction and this new proof system is to enable an easy transformation into a threshold protocol, something previous designs have not achieved. To this end, we present our VOPRF in a modular way based on different subroutines. We show how to replace these subroutines with their threshold counterparts, using simulation-based arguments. This results in the first threshold VOPRF from isogenies and one of the first threshold VOPRFs in the post-quantum literature. In contrast to other post-quantum threshold VOPRF designs, our construction has input and output size independent of the number of server parties and furthermore is robust, while other designs rely on aborts in the presence of malicious parties.

Note: This article is the full version of a paper accepted at PKC 2026.

Metadata

Available format(s): PDF
Category: Cryptographic protocols
Publication info: A minor revision of an IACR publication in PKC 2026
Keywords: Oblvious pseudo-random functions threshold schemes isogeny-based cryptography effective group actions
Contact author(s): robi pedersen @ protonmail com
History: 2026-03-11: approved; 2026-03-09: received; See all versions
Short URL: https://ia.cr/2026/489
License: CC BY

BibTeX

@misc{cryptoeprint:2026/489,
      author = {Robi Pedersen},
      title = {Threshold Oblivious Pseudorandom Functions from Isogeny Group Actions},
      howpublished = {Cryptology {ePrint} Archive, Paper 2026/489},
      year = {2026},
      url = {https://eprint.iacr.org/2026/489}
}