Paper 2024/329

How to Validate a Verification?

Abstract

This paper introduces \textsl{signature validation}, a primitive allowing any \underline{t}hird party $T$ (\underline{T}héodore) to verify that a \underline{v}erifier $V$ (\underline{V}adim) computationally verified a signature $s$ on a message $m$ issued by a \underline{s}igner $S$ (\underline{S}arah). A naive solution consists in sending by Sarah $x=\{m,{\sigma }_s\}$ where ${\sigma }_s$ is Sarah's signature on $m$ and have Vadim confirm reception by a signature ${\sigma }_v$ on $x$. Unfortunately, this only attests \textsl{proper reception} by Vadim, i.e. that Vadim \textsl{could have checked} $$ and not that Vadim \textsl{actually verified} $$. By ``actually verifying'' we mean providing a proof or a convincing argument that a program running on Vadim's machine checked the correctness of $$. This paper proposes several solutions for doing so, thereby providing a useful building-block in numerous commercial and legal interactions for proving informed consent.