Paper 2025/1120 Original: eprint.iacr.org/2025/1120 ↗

Traceable Secret Sharing Schemes for General Access Structures

Abstract

Traceable secret sharing complements traditional schemes by enabling the identification of parties who sell their shares. In the model introduced by Boneh, Partap, and Rotem [CRYPTO’24], a group of corrupted parties generates a reconstruction box $R$ that, given enough valid shares as input, reconstructs the secret. The goal is to trace $R$ back to at least one of the corrupted parties using only black-box access to it. While their work provides efficient constructions for threshold access structures, it does not apply to the general case. In this work, we extend their framework to general access structures and present an information-theoretic traceable scheme supporting them. In the course of our construction, we also contribute to the study of anonymous secret sharing, a notion recently introduced by Bishop et al. [CRYPTO’25], which strengthens classical secret sharing by requiring that shares do not reveal the identities of the parties holding them. We further advance this area by proposing new and stronger definitions, and presenting an anonymous scheme for general access structures that satisfies them.