CAISED: A Protocol for Cast-as-Intended Verifiability with a Second Device

Abstract

AbstractNumerous approaches for cast-as-intended verifiability have been proposed in the literature on electronic voting, balancing practical aspects and security guarantees in different ways. One of the well-established methods involves the use of a second device that allows voters to audit their submitted ballots. This approach offers several benefits, including support for flexible ballot and election types and an intuitive user experience. Moreover, solutions based on this approach are generally adaptable to a range of existing voting protocols, rather than being restricted to a particular election scheme. This approach has been successfully implemented in real-life elections, such as in Estonia [18].In this work, we improve the existing solutions for cast-as-intended verifiability based on the use of a second device. We propose a solution that preserves the advantageous practical properties outlined above, while providing stronger security guarantees. Our method does not increase the risk of vote selling compared to the underlying voting protocol to be augmented, and it requires only comparatively weak trust assumptions to achieve this. It can be combined with various voting protocols, including commitment-based systems that provide everlasting privacy.Overall, our work offers a new option to strengthen cast-as-intended and end-to-end verifiability for real-world Internet elections.