MICHEL MARTIN, HOST:
We want to talk more about election security. Apart from the allegation we heard earlier, there are concerns about election security, especially after reports of interference by foreign actors in 2016. Now some states are moving away from electronic voting machines and returning to paper ballots all in the name of security. But, as Alan Yu of member station WHYY reports, making that switch isn't always easy.
ALAN YU, BYLINE: SarahRae Sisson became the director of elections in Susquehanna County in northeastern Pennsylvania about two years ago. When she realized that the county still used paper ballots in all elections, she thought that wasn't great.
SARAHRAE SISSON: I had made little comments about how, you know, we were not in the 21st century because we were still paper.
YU: But the more she learned about how to keep elections safe, she realized that using paper ballots is, actually, a good thing.
SISSON: You can't hack a paper ballot or change anything about it.
YU: Susquehanna County turns out to be ahead of most of the other counties in the state because it already relies on paper ballots that election officials can audit if they suspect any kind of attack. The vast majority of Pennsylvania's counties use electronic voting machines that don't leave a paper trail.
ANDREW APPEL: It would really be comforting to be able to say we shouldn't worry, but these machines are hackable.
YU: That's Andrew Appel, a computer science professor at Princeton University.
APPEL: Anyone who has physical access to that voting machine any time in the 20 years before the election can install a vote-stealing program in it.
YU: In 2008, he demonstrated just how vulnerable voting machines can be by hacking into one in under seven minutes. Two counties in Pennsylvania still use that exact same model of voting machine. While the machines may be vulnerable, actually changing the outcome of an election is much more complicated. Election officials say no hacker would have such unfettered access to voting machines. Kenneth Lawrence chairs the elections board in Montgomery County.
KENNETH LAWRENCE: All of our machines are sealed, and they're headquartered at a secure location with security.
YU: There are other vulnerabilities - voter registration systems, the ballots, election board websites. Andrew Appel at Princeton says computers are inherently vulnerable to manipulation compared to paper ballots.
APPEL: We need to make sure that whatever piece of paper the voter saw with their votes on it or marked - even better - is the one that's a ballot of record for a recount.
YU: Appel argues it's fine to let computers do the counting, but having a paper trail in case of a hack or even a faulty machine is essential. Pennsylvania Governor Tom Wolf has said counties should have more secure paper-based voting systems in time for the 2020 election. But local officials say making that switch won't be easy. Lisa Deeley is a city commissioner in Philadelphia and is in charge of elections. Pennsylvania tests and certifies voting systems that counties can choose from.
LISA DEELEY: Right now, the state has only certified one system, so you're talking about the city of Philadelphia making a legacy purchase of millions of dollars.
YU: Deeley says she doesn't want to buy thousands of new machines until she has more than one choice. For now, Deeley and her colleagues around the state are doing what they can to reassure voters that their ballots will be safe.
For NPR News, I'm Alan Yu in Philadelphia. Transcript provided by NPR, Copyright NPR.