Then, when counting the votes for each candidate we display the running product of all the primes counted for that candidate as a "checksum", or "check product". This retains privacy while allowing individual voters to easily verify that their vote was counted by simply dividing their party's checksum by their prime ballot number and confirming that it is a factor of the check product. By displaying a running product of votes, you can also verify that your vote was not counted before you voted. Additionally, this prevents double counting because the "checksum" for N primes must match exactly N votes and no two candidates can share a factor. By issuing sequences of primes to certain regions, you can get some metrics by state.
Then you institute a rule that if some % of primes dispute that theirs was counted correctly, a recount is automatically triggered.