Verifiable voting systems have been around for a while. There are two primary approaches for achieving verifiability: a) through end-to-end verifiable voting (E2E-V) systems that offer cryptographic guarantees of correctness, and b) through risk-limiting audit systems that do not rely on cryptography but verify the tally reported by an electronic vote tabulation system against voter-verified paper records (VVPRs). However, while end-to-end verifiable methods lack easy methods of recovery in case elections fail to verify, risk-limiting audit based methods usually require the electorate to trust the post-election custody chain of the VVPRs. In this paper we examine recovery from elections in dual voting, which combines the formal guarantees of E2E-V with the simplicity of VVPR-based audit. We argue that large public elections should not only be publicly verifiable, but, in case of verification failures, there should also be transparent methods of recovery without necessarily re-running entire elections. We focus on multi-polling booth elections and formally define the concept of recoverability for such protocols. Informally, our formulation captures the ability to verifiably identify the polling booths contributing to verification failures, and the partial tally contributed by the other booths, without leaking any additional information. This enables possible recovery through limited re-polling, without necessitating a complete re-run of the election or privileging the paper tally over the electronic one. We also propose a multi-polling booth voting protocol called \emph{OpenVoting} that achieves our proposed recoverability requirements.

翻译：可验证投票系统已存在一段时间。实现可验证性主要有两种方法：一是通过端到端可验证投票（E2E-V）系统提供密码学上的正确性保证；二是通过风险限制审计系统，该方法不依赖密码学，而是将电子投票计票系统报告的计票结果与选民核实的纸质记录（VVPR）进行核对。然而，端到端可验证方法在选举无法通过验证时缺乏简便的恢复方法，而基于风险限制审计的方法通常要求选民信任选举后的VVPR保管链。本文研究双投票系统中选举的恢复问题，该方法结合了E2E-V的形式化保证与基于VVPR审计的简便性。我们认为，大型公共选举不仅应具有公开可验证性，而且在验证失败时，应存在透明的恢复方法，无需完全重新举行选举。我们聚焦于多投票站选举，并正式定义此类协议的可恢复性概念。非正式地说，我们的形式化描述能够以可验证的方式识别导致验证失败的投票站，以及其他投票站提供的部分计票结果，同时不泄露任何额外信息。这使得通过有限重新投票实现恢复成为可能，既无需完全重选，也无需赋予纸质计票结果高于电子计票结果的优先权。我们还提出一种名为\emph{OpenVoting}的多投票站投票协议，该协议实现了我们提出的可恢复性要求。