Yvo Desmedt date:2023/3/10 TITLE:  Framing and Realistic Secret Sharing

The use of Game Theory to Secret Sharing has lead to Rational Secret Sharing (RSS). It claims that from an economic viewpoint it would be irrational for parties to reveal their shares, and so the secret will never be reconstructed! In this presentation we present Realistic Secret Sharing, which we contrast with Rational Secret Sharing (RSS). We do not claim that RSS is wrong, but that it is restricted to a limited number of settings. In the presentation we explain when these settings occur and when not. In the last case we have realistic secret sharing, and the secret will be reconstructed! In the 2nd part of this talk, we introduce forensics aspects of secret sharing. Suppose that a dealer makes a legal will and distributes shares to family members using Shamir Secret Sharing scheme. Obviously, some of these parties are interested in having a preliminary (i.e., before the death of the dealer), unauthorized, reconstruction of the secret. When the will is released preliminary, one may want to trace who the parties were that illegally reconstructed the secret. Unfortunately such a forensics analysis has no value because the parties releasing the will can frame others. Part of this research was done while visiting University of Auckland. This talk is open to anyone familiar with linear algebra only. The talk is based on papers published in GameSec 2019 and IEEE Trans. Inf. Forensics Security 2021.