Dealer-Free Threshold Changeability in Secret Sharing Schemes

This paper proposes a dealer-free threshold changeable construction for secret sharing schemes. In practice, the adversary’s ability might be enhanced over time, for instance by compromising more players. This problem can be resolved only by increasing the threshold. In the literature, there exist some techniques to address this issue. These solutions either have a large storage requirement or are limited to a predefined threshold modification. In addition, they increase the threshold at the side of the combiner with some mathematical assumptions. We apply two secure multiparty computation techniques [2, 16] to tackle these problems. In our constructions, participants do not need to save any information or extra shares ahead of time, and the threshold can be changed multiple times to any arbitrary values. Moreover, the presented protocols are unconditionally secure and realize a proactive secret sharing scheme.