Peel and Vote: A Paper Ballot Design for Publicly Verifiable Risk-Limiting Audits

Post-election Risk-Limiting Audits (RLAs) provide statistical guarantees of election outcomes by hand-counting randomly selected paper ballots. However, standard RLAs assume that ballots remain unaltered in storage between election day and the audit, but voters cannot verify this assumption. Prior frameworks, such as VAULT (E-VOTE-ID 2019), attempt to make the audit process verifiable, but they require the public to trust the Election Authority (EA) to honestly sample ballots at random and correctly interpret the voters’ choices into cryptographic commitments. Furthermore, they are typically ballot-level, requiring a 1-to-1 mapping between individual paper ballots and digital records. The EA also needs to interactively open commitments during the audit. To address these limitations, we propose the first verifiable batch-level RLA scheme, which shifts the trust anchor from the EA directly to the voter and operates on groups of ballots (batches) to eliminate individual tracking hurdles. Our scheme introduces a peel-and-vote paper ballot design with removable flaps containing pre-printed cryptograms. A voter selects a candidate by removing the corresponding flap, and retains the flap as a receipt, while the same cryptogram printed on the receipt is also published on a bulletin board. In our scheme, a batch contains a group of cryptographically related ballots that are randomly distributed across the precincts before the election. Once all cryptograms in a batch are published, anyone can independently compute the tally for that batch, achieving a self-tallying property. Intuitively, our scheme transforms a national-scale election into many smaller self-tallying elections: one for each batch. Based on historical US election data, we show that when the ballot loss rates remain below 0.5%, the scheme enables tally verification for 61% of randomly selected ballots with a batch size of 100, or 37% with a batch size of 200. These figures are substantially higher than the 0.01–0.3% sampling coverage typically achieved in RLAs. This improvement stems from the fact that auditing is built directly into the paper ballot design in our scheme as an always-on feature, rather than being treated as an optional manual post-election process.