Paper 2025/850 Original: eprint.iacr.org/2025/850 ↗

Succinct Computational Secret Sharing for Monotone Circuits

Abstract

Secret sharing is a cornerstone of modern cryptography, underpinning the secure distribution and reconstruction of secrets among authorized participants. In these schemes, succinctness—measured by the size of the distributed shares—has long been an area of both great theoretical and practical interest, with large gaps between constructions and best known lower bounds. In this paper, we present a novel computational secret sharing scheme for monotone Boolean circuits that achieves substantially shorter share sizes than previously known constructions in the standard model. Our scheme attains a public share size of $n + \mathsf{poly}(\lambda, \log |C|)$ and a user share size of $\lambda$, where n denotes the number of users, $C$ is the monotone circuit and $\lambda$ is the security parameter, thus effectively eliminating the dependence on the circuit size. This marks a significant improvement over earlier approaches, which exhibited share sizes that grew with the number of gates in the circuit. Our construction makes use of indistinguishability obfuscation and injective one-way functions.