[3131s]

Just have the electronic system return a clearly labeled ballot to the voter, which would be verified and turned in before leaving. A physical count can be used to confirm the electronic count or vice-versa (physical counting has vulnerabilities too).

[JshWright]

New York uses the reverse of that. You fill out a paper ballot, which then gets fed into a machine for counting. A random sample (of sufficient size) of the paper ballots are then counted to verify the electronic results.