Testifying before the House Subcommittee on Information Technology, Appel told members of Congress that it is critical to have a system in place to audit votes cast to ensure accuracy and confidence in the electoral system. Most U.S. states have some sort of paper backup that can be used to resolve questions about the vote, but Appel said that states and counties using direct-recording electronic voting machines, commonly called touchscreens, do not.

“There’s no paper ballot to recount,” said Appel, the Eugene Higgins Professor of Computer Science, according to his written testimony. “After the voter touches the screen, we have to rely on the computer – that is, we have to rely on whatever program is installed in the computer that day – to print out the true totals that night when the polls close. “

Appel, whose research focuses on software verification and applied computer security, is a noted expert on voting machines. Besides writing a number of scientific papers on voting security, Appel demonstrated in 2009 in New Jersey Superior Court how to hack a machine.

“Colleagues and students at Princeton University and elsewhere have demonstrated the same principle on several different models,” Appel said. “This is not just one glitch in one manufacturer’s machine, it’s the very nature of computers.”

Appel testified that Congress has fixed similar problems in the past. After the infamous recount of the 2000 election, Congress banned the use of punch-card voting ballots.

Right now, Appel said, most states require a paper record in addition to the computer vote. The most common form is a paper ballot which is marked by the voter and then fed into a computerized scanner.

“That very paper ballot marked by the voter drops into a sealed ballot box under the opscan machine,” he said. “That is the ballot of record, and it can be recounted by hand in a way that we can trust.”

As a temporary measure, Appel recommended that election officials take care not connect voting machines or election administration computers to the internet. But he said these steps won’t eliminate the threat of local tampering.

“So what we must do as soon as possible after November is to adopt nationwide what 40 states have already done: paper ballots, marked by the voter, countable by computer if you like but recountable by hand,” he said.

Appel’s written testimony concludes with “Ten Things Election Officials Can Do to Help Secure and Inspire Confidence in This Fall’s Elections.” Full testimony available at: https://oversight.house.gov/hearing/cybersecurity-ensuring-integrity-ballot-box/