On Distributed Multi-User Secret Sharing with Multiple Secrets per User

TL;DR

This paper extends distributed multi-user secret sharing to the case where users demand multiple secrets, analyzing access structures, secrecy conditions, and communication bounds, and characterizing the capacity region for general access structures.

Contribution

It generalizes previous work by considering multiple secrets per user, establishes necessary secrecy conditions, links access structures to t-disjunct matrices, and derives bounds and capacity results.

Findings

Identifies necessary conditions for weak secrecy in multi-secret sharing

Connects access structures to t-disjunct matrix constructions

Derives bounds on communication complexity and characterizes capacity region

Abstract

We consider a distributed multi-user secret sharing (DMUSS) setting in which there is a dealer, $n$ storage nodes, and $m$ secrets. Each user demands a $t$-subset of $m$ secrets. Earlier work in this setting dealt with the case of $t=1$; in this work, we consider general $t$. The user downloads shares from the storage nodes based on the designed access structure and reconstructs its secrets. We identify a necessary condition on the access structures to ensure weak secrecy. We also make a connection between access structures for this problem and $t$-disjunct matrices. We apply various $t$-disjunct matrix constructions in this setting and compare their performance in terms of the number of storage nodes and communication complexity. We also derive bounds on the optimal communication complexity of a distributed secret sharing protocol. Finally, we characterize the capacity region of the DMUSS problem when the access structure is specified.