Paper 2018/083

Flaws in a Verifiably Multiplicative Secret Sharing Scheme from ICITS 2017

Maki Yoshida and Satoshi Obana

Abstract

In this paper, we point out flaws in an existing verifiably multiplicative secret sharing (VMSS) scheme. Namely, we show that a scheme proposed by Yoshida and Obana presented at ICITS 2017 is insecure against an adversary who corrupts a single player. We then show that in the model of ICITS 2017 which restricts the decoder additive, the error-free verification is impossible. We further show that by allowing a general class of decoders which include a linear one, the scheme is error-free.